《卸甲笔记》-限定查询与排序显示
2023-09-14 09:03:16 时间
2 统计出基本工资高于1500元的全部雇员信息
Oracle
SQL select * from emp where sal 1500; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30scott=# select * from emp where sal 1500; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+--------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (7 rows)3查询出所有基本工资小于等于2000元的全部雇员信息
OracleSQL select * from emp where sal =2000; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20scott=# select * from emp where sal =2000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+---------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (8 rows)4根据之前的查询结果发现SMITH的工资 最低，所以现在希望可以取得SMITH的详细资料
OracleSQL select * from emp where ename=SMITH; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20PPAS
scott=# select * from emp where ename=SMITH; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-------+------+--------------------+--------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 (1 row)5查询出所有业务员（CLERK）的雇员信息
OracleSQL select * from emp where job=CLERK; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7934 MILLER CLERK 7782 23-JAN-82 1300 10PPAS
scott=# select * from emp where job=CLERK; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (4 rows)6为了和其他职位的雇员对比，现在决定查询所有不是业务员的雇员信息
OracleSQL select * from emp where job CLERK; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7566 JONES MANAGER 7839 02-APR-81 2975 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7566 JONES MANAGER 7839 02-APR-81 2975 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20scott=# select * from emp where job CLERK; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (10 rows) scott=# select * from emp where job!=CLERK; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (10 rows)7查询出工资范围在1500~3000（包含1500和3000）元的全部雇员信息
OracleSQL select * from emp where sal =1500 and sal =3000; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20scott=# select * from emp where sal =1500 and sal =3000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+--------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (7 rows)8查询职位是销售人员，并且基本工资高于1200元的所有雇员信息
OracleSQL select * from emp where job=SALESMAN and sal 1200; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30PPAS
scott=# select * from emp where job=SALESMAN and sal 1200; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 (4 rows)9要求查询出10部门中的经理或者20部门中的业务员的信息
OralceSQL select * from emp 2 where (deptno=10 and job=MANAGER) or (deptno=20 and job=CLERK); EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7876 ADAMS CLERK 7788 23-MAY-87 1100 20PPAS
scott=# select * from emp scott-# where (deptno=10 and job=MANAGER) or (deptno=20 and job=CLERK); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+---------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 (3 rows)10查询不是业务员且基本工资大于2000元的全部雇员信息
OracleSQL select * from emp 2 where job !=CLERK and sal 2000; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20
scott-# where job !=CLERK and sal 2000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+------+-------- 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (6 rows) scott=# select * from emp scott-# where job CLERK and sal 2000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+------+-------- 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (6 rows) scott=# select * from emp scott-# where not(job=CLERK or sal =2000); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+------+-------- 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (6 rows)范围查询：BETWEEN 最小值 AND 最大值
11使用between … and 操作符查询出工资范围在1500~3000（包括1500和3000元的全部雇员信息）
OracleSQL select * from emp where sal between 1500 and 3000; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7 rows selected.PPAS
scott=# select * from emp where sal between 1500 and 3000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+--------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (7 rows)12查询出在1981年雇佣的全部雇员信息
OracleSQL select * from emp where hiredate between 01-Jan-1981 and 31-Dec-1981; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7566 JONES MANAGER 7839 02-APR-81 2975 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20PPAS
scott=# select * from emp where hiredate between 01-1-1981 and 31-12-1981; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (10 rows)判断内容是否为null:IS NULL 、IS NOT NULL
13 使用==进行NULL比较
OracleSQL select * from emp where comm=null and empno=7369; no rows selectedPPAS
scott=# select * from emp where comm=null and empno=7369; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----+-----+----------+-----+------+-------- (0 rows)14查询出所有领取佣金的雇员的完整信息
OracleSQL select * from emp where comm is not null; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 SQL select * from emp where not comm is null; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30PPAS
scott=# select * from emp where comm is not null; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 (4 rows) scott=# select * from emp where not comm is null; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 (4 rows)15 查询所有不领取佣金的雇员的完整信息
OracleSQL select * from emp where comm is null; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30 7902 FORD ANALYST 7566 03-DEC-81 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7934 MILLER CLERK 7782 23-JAN-82 1300 10scott=# select * from emp where comm is null; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (10 rows)16列出所有不领取奖金，同时基本工资大于2000元的全部雇员信息
OracleSQL select * from emp where comm is null and sal 2000; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20scott=# select * from emp where comm is null and sal 2000; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+------+-------- 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (6 rows)17 查找不收取佣金 或 收取的佣金低于100元的员工
OracleSQL select * from emp where comm is null or comm EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10scott=# select * from emp where comm is null or comm empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (11 rows)18查找收取佣金的员工的不同工作
OracleSQL select distinct job from emp where comm is not null; --------- SALESMANPPAS
scott=# select distinct job from emp where comm is not null; job ---------- SALESMAN (1 row)列表范围查找：IN 、NOT IN
19查询出雇员编号是7369、7788/7566的雇员信息
OracleSQL select * from emp where empno=7369 or empno=7788 or empno=7566; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20PPAS
scott=# select * from emp where empno=7369 or empno=7788 or empno=7566; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+---------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 (3 rows)20 通过IN操作符指定查询范围
OracleSQL select * from emp where empno IN(7369,7788,7566); EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20PPAS
scott=# select * from emp where empno IN(7369,7788,7566); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+---------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 (3 rows)21查询除了7369、7788、7566之外的雇员信息
OracleSQL select * from emp where empno NOT IN(7369,7788,7566); EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7839 KING PRESIDENT 17-NOV-81 5000 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10scott=# select * from emp where empno NOT IN(7369,7788,7566); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (11 rows)注意：在使用NOT IN操作符时列表不能有NULL
22在使用NOT IN操作符中 设置 null
OracleSQL select * from emp where empno NOT IN(7369,7788,null); no rows selectedPPAS
scott=# select * from emp where empno NOT IN(7369,7788,null); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----+-----+----------+-----+------+-------- (0 rows)模糊查询：LIKE、NOT LIKE
23查询出雇员姓名是以S开头的全部雇员信息
OracleSQL select * from emp where ename like S%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20PPAS
scott=# select * from emp where ename like S%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+---------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 (2 rows)24查询姓名的第2个字母是M的全部雇员信息
OracleSQL select * from emp where ename like _M%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20PPAS
scott=# select * from emp where ename like _M%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-------+------+--------------------+--------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 (1 row)25查询姓名中任意位置包含字母F的雇员信息
OracleSQL select * from emp where ename like %F%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20PPAS
scott=# select * from emp where ename like %F%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+---------+------+--------------------+---------+------+-------- 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 (1 row)26查询姓名长度为6或者超过6的雇员信息
OracleSQL select * from emp where ename like ______%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7934 MILLER CLERK 7782 23-JAN-82 1300 10PPAS
scott=# select * from emp where ename like ______%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+----------+------+--------------------+---------+---------+-------- 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (3 rows)27查询出基本工资中包含 1或者在81年雇佣的全部雇员信息
OracleSQL select * from emp where sal like %1% or hiredate like %81%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7566 JONES MANAGER 7839 02-APR-81 2975 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7900 JAMES CLERK 7698 03-DEC-81 950 30 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10PPAS
scott=# select * from emp where sal like %1% or hiredate like %81%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (12 rows)28不设置查询关键字标识查询全部
OracleSQL select * from emp where empno like %% or ename like %% or job like %% 2 or hiredate like %% or sal like %% or comm like %%; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10 14 rows selected.PPAS
scott=# select * from emp where empno like %% or ename like %% or job like %% scott-# or hiredate like %% or sal like %% or comm like %%; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (14 rows)29找出部门10中所有经理（MANAGER）,部门20中所有业务员（CLERK），既不是经理又不是业务员但薪金大于2000元的所有员工的详细资料，并且要求 这些雇员的姓名中包含字母S或字母K
OracleSQL select * from emp 2 where ((deptno=10 and job=MANAGER) or (deptno=20 and job=CLERK) 3 or (job not in (MANAGER,CLERK) and sal 2000)) 4 and (ename like %S% or ename like %K%); EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7876 ADAMS CLERK 7788 23-MAY-87 1100 20PPAS
scott=# select * from emp scott-# where ((deptno=10 and job=MANAGER) or (deptno=20 and job=CLERK) scott(# or (job not in (MANAGER,CLERK) and sal 2000)) scott-# and (ename like %S% or ename like %K%); empno | ename | job | mgr | hiredate | sal | comm | deptno -------+-------+-----------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 (5 rows)对结果排序
30 查询员工的完整信息，并且按照级别工资由高到低进行排序
OracleSQL select * from emp order by sal desc; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7934 MILLER CLERK 7782 23-JAN-82 1300 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7900 JAMES CLERK 7698 03-DEC-81 950 30 7369 SMITH CLERK 7902 17-DEC-80 800 20scott=# select * from emp order by sal desc; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 (14 rows)31利用序号设置排序列
OracleSQL select empno,ename,sal,job from emp order by 3 desc; EMPNO ENAME SAL JOB ---------- -------------------- ---------- ------------------ 7839 KING 5000 PRESIDENT 7902 FORD 3000 ANALYST 7788 SCOTT 3000 ANALYST 7566 JONES 2975 MANAGER 7698 BLAKE 2850 MANAGER 7782 CLARK 2450 MANAGER 7499 ALLEN 1600 SALESMAN 7844 TURNER 1500 SALESMAN 7934 MILLER 1300 CLERK 7521 WARD 1250 SALESMAN 7654 MARTIN 1250 SALESMAN EMPNO ENAME SAL JOB ---------- -------------------- ---------- ------------------ 7876 ADAMS 1100 CLERK 7900 JAMES 950 CLERK 7369 SMITH 800 CLERK 14 rows selected.PPAS
scott=# select empno,ename,sal,job from emp order by 3 desc; empno | ename | sal | job -------+--------+---------+----------- 7839 | KING | 5000.00 | PRESIDENT 7902 | FORD | 3000.00 | ANALYST 7788 | SCOTT | 3000.00 | ANALYST 7566 | JONES | 2975.00 | MANAGER 7698 | BLAKE | 2850.00 | MANAGER 7782 | CLARK | 2450.00 | MANAGER 7499 | ALLEN | 1600.00 | SALESMAN 7844 | TURNER | 1500.00 | SALESMAN 7934 | MILLER | 1300.00 | CLERK 7654 | MARTIN | 1250.00 | SALESMAN 7521 | WARD | 1250.00 | SALESMAN 7876 | ADAMS | 1100.00 | CLERK 7900 | JAMES | 950.00 | CLERK 7369 | SMITH | 800.00 | CLERK (14 rows)32按照级别工资由低到高排序
OracleSQL select * from emp order by sal; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7900 JAMES CLERK 7698 03-DEC-81 950 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7934 MILLER CLERK 7782 23-JAN-82 1300 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 14 rows selected. SQL select * from emp order by sal asc; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7900 JAMES CLERK 7698 03-DEC-81 950 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7934 MILLER CLERK 7782 23-JAN-82 1300 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 14 rows selected.PPAS
scott=# select * from emp order by sal; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 (14 rows) scott=# select * from emp order by sal asc; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 (14 rows)33查询出所有业务员（CLERK）的详细资料，并且按照基本工资由低到高排序
OracleSQL select * from emp where job=CLERK order by sal; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7369 SMITH CLERK 7902 17-DEC-80 800 20 7900 JAMES CLERK 7698 03-DEC-81 950 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7934 MILLER CLERK 7782 23-JAN-82 1300 10PPAS
scott=# select * from emp where job=CLERK order by sal; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-------+------+--------------------+---------+------+-------- 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 (4 rows)34查询出所有雇员信息，要求按照基本工资由高到低排序，如果工资相等则按照雇佣日期由早到晚进行排序
OracleSQL select * from emp order by sal desc,hiredate asc; EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7566 JONES MANAGER 7839 02-APR-81 2975 20 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7934 MILLER CLERK 7782 23-JAN-82 1300 10
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE ---------- -------------------- ------------------ ---------- ------------ SAL COMM DEPTNO ---------- ---------- ---------- 7900 JAMES CLERK 7698 03-DEC-81 950 30 7369 SMITH CLERK 7902 17-DEC-80 800 20 14 rows selected.PPAS
scott=# select * from emp order by sal desc,hiredate asc; empno | ename | job | mgr | hiredate | sal | comm | deptno -------+--------+-----------+------+--------------------+---------+---------+-------- 7839 | KING | PRESIDENT | | 17-NOV-81 00:00:00 | 5000.00 | | 10 7902 | FORD | ANALYST | 7566 | 03-DEC-81 00:00:00 | 3000.00 | | 20 7788 | SCOTT | ANALYST | 7566 | 19-APR-87 00:00:00 | 3000.00 | | 20 7566 | JONES | MANAGER | 7839 | 02-APR-81 00:00:00 | 2975.00 | | 20 7698 | BLAKE | MANAGER | 7839 | 01-MAY-81 00:00:00 | 2850.00 | | 30 7782 | CLARK | MANAGER | 7839 | 09-JUN-81 00:00:00 | 2450.00 | | 10 7499 | ALLEN | SALESMAN | 7698 | 20-FEB-81 00:00:00 | 1600.00 | 300.00 | 30 7844 | TURNER | SALESMAN | 7698 | 08-SEP-81 00:00:00 | 1500.00 | 0.00 | 30 7934 | MILLER | CLERK | 7782 | 23-JAN-82 00:00:00 | 1300.00 | | 10 7521 | WARD | SALESMAN | 7698 | 22-FEB-81 00:00:00 | 1250.00 | 500.00 | 30 7654 | MARTIN | SALESMAN | 7698 | 28-SEP-81 00:00:00 | 1250.00 | 1400.00 | 30 7876 | ADAMS | CLERK | 7788 | 23-MAY-87 00:00:00 | 1100.00 | | 20 7900 | JAMES | CLERK | 7698 | 03-DEC-81 00:00:00 | 950.00 | | 30 7369 | SMITH | CLERK | 7902 | 17-DEC-80 00:00:00 | 800.00 | | 20 (14 rows)
CE修改器入门：精确数值扫描 附加`Tutorial-i386.exe进程`后,我们点击教程的下一步按钮，接着继续第二关，第二关的作用还是很简单的，主要目的是遍历出我们想要的动态数据，比如角色的生命，人物的魔法等，都会用到精确扫描，可以说这一关是既简单又实用的东西，也是今后制作中最常用的环节，接着我们看下`Tutorial-i386.exe程序`对这一关通关流程的描述:
CE修改器入门：未知数值扫描 经过第二关的练习，你已经理解了如何利用 精确数值 扫描查找数值了，让我们进行下一步，本关主要用来搜索进度条，人物血条等，因为这些数据通常是一个进度条，我们无法直接看到的数据，此时可以通过变更的数据一步步筛选找到动态地址。
测试编程笔试题No.1-输入表格列的英文名称，返回其对应的数字序号 同一个字母，在不同的位置，对应的值不一样，字母A在个位对应的是1，在十位对应的是26 ，因此，联想到了进制的移位运算和进制之间的转换。
Oracle数据库之五 限定查询和排序显示 Oracle数据库之五 限定查询和排序显示五、限定查询和排序显示5.1、限定查询5.1.1 认识限定查询例如：如果一张表中有 100w 条数据，一旦执行了 “ SELECT * FROM 表 ” 语句之后，则将在屏幕上显示表中全部数据行的记录，这样既不方便浏览，也可能造成死机的问题，所以此时就必须对查询的结果进行筛选，只选出对自己有用的数据即可，那么就可以通过 WHERE 指定查询的筛选条件。
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