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查询当前数据库名,表名

数据库 查询 当前 表名
2023-09-27 14:28:06 时间

MySQL

  1)显示所有数据库

  show database;

  2)显示所有表

  show tables;

  3)显示表结构

  desc 表名

 

SQL Server

  当前数据库名:  

  select db_name() as databasename
  所有数据库名:
  select name from master..sysdatabases order by name

  查询所有表:

  select * from sysobjects where xtype='U'

  某个数据库中所有的表名:

  select name from sysobjects where xtype='u' order by name

   查询表结构信息:

SELECT (case when a.colorder=1 then d.name else null end) 表名, 
 a.colorder 字段序号,a.name 字段名,
 (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) 标识,
 (case when (SELECT count(*) FROM sysobjects 
 WHERE (name in (SELECT name FROM sysindexes 
 WHERE (id = a.id) AND (indid in 
 (SELECT indid FROM sysindexkeys 
 WHERE (id = a.id) AND (colid in 
 (SELECT colid FROM syscolumns WHERE (id = a.id) AND (name = a.name))))))) 
 AND (xtype = 'PK'))>0 then '√' else '' end) 主键,b.name 类型,a.length 占用字节数, 
 COLUMNPROPERTY(a.id,a.name,'PRECISION') as 长度, 
 isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as 小数位数,(case when a.isnullable=1 then '√'else '' end) 允许空, 
 isnull(e.text,'') 默认值,isnull(g.[value], ' ') AS [说明]
 FROM  syscolumns a
 left join systypes b on a.xtype=b.xusertype 
 inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties'
 left join syscomments e on a.cdefault=e.id 
 left join sys.extended_properties g on a.id=g.major_id AND a.colid=g.minor_id
 left join sys.extended_properties f on d.id=f.class and f.minor_id=0
 where b.name is not null
 --WHERE d.name='要查询的表' --如果只查询指定表,加上此条件
 order by a.id,a.colorder

 

oracle

(1) 启动 监听

        lsnrctl start;

(2)进入sqlplus界面

       sqlplus  /nolog

       SQL>conn sys/jiaxiaoai@orcl as sysdba;

(3)启动数据库实例

       SQL>startup;

(4)查看当前所有的数据库
    
    select name from v$database;

(5)查看哪些用户拥有sysdba、sysoper权限

        select * from V_$PWFILE_USERS;

        show user;查看当前数据库连接用户

(6)进入某个数据库:database 数据库名;

       查看数据库结构:desc v$database;

(7)查看所有用户实例:

        select instance_name from v$instance;

 (8)查看当前库的所有数据表

       select table_name from all_tables;

       select table_name from user_tables;

       select table_name from all_tables where owner='用户名';

 (9)查看表结构

        desc 表名;

 (10)增加数据库用户

         create user 用户名 identified by 密码 default tablespace users Temporary TABLESPACE Temp;

 (11)用户授权

         grant connect,resource,dba to 用户名;

         grant sysdba to 用户名;

 (12)更改数据库用户密码

         alter user 用户名 identified by 密码;