0 总结

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• updata on 20200506：修改相关格式；在单层循环中，增加test的创表语句

1.单层循环

• 先定义测试表

create table test(location_id int ,location_name varchar(10));

• 再编写存储过程，其中涉及到循环的使用。我们欲通过这个存储过程，来达到往表中插入数据的效果。

drop procedure if exists test_loop;
delimiter //
create procedure test_loop()
begin
	declare i int default 1;
	while i<10
	do
		insert into test values(i,concat('hangzhou',i));
		set i=i+1;
	end while;
	commit;
end //
delimiter ;

• 接着检验输出

mysql> select * from test;
Empty set (0.00 sec)

mysql> call test_loop();
Query OK, 0 rows affected (0.35 sec)

mysql> select * from test;
+-------------+---------------+
| location_id | location_name |
+-------------+---------------+
|           1 | hangzhou1     |
|           2 | hangzhou2     |
|           3 | hangzhou3     |
|           4 | hangzhou4     |
|           5 | hangzhou5     |
|           6 | hangzhou6     |
|           7 | hangzhou7     |
|           8 | hangzhou8     |
|           9 | hangzhou9     |
+-------------+---------------+
9 rows in set (0.00 sec)

发现存储过程调用成功，即循环调用成功。

2.双层循环

• 创建表

CREATE TABLE `dim_time` (
  `TimeKey` int(11) NOT NULL,
  `Hour` tinyint(4) DEFAULT NULL,
  `Minute` tinyint(4) DEFAULT NULL,
  PRIMARY KEY (`TimeKey`)
)

• 编写存储过程

drop procedure if exists insertValueIntoDimTime;
delimiter //
create procedure insertValueIntoDimTime()
begin
	declare hour int default 0;
	declare min int default 0;	
		while hour < 24
		do
			while min < 60
			do
				insert into dim_time values(hour*100+min,hour,min);
				set min=min+1;
			end while;
			set min = 0;
			set hour = hour+1;
		end while;
end //
delimiter ;

• 运行存储过程

mysql> call insertValueIntoDimTime;
Query OK, 1 row affected (22.12 sec)

• 验证输出

mysql> select count(*) from dim_time;
+----------+
| count(*) |
+----------+
|     1440 |
+----------+
1 row in set (0.02 sec)

mysql> select * from dim_time order by timekey limit 10;
+---------+------+--------+
| TimeKey | Hour | Minute |
+---------+------+--------+
|       0 |    0 |      0 |
|       1 |    0 |      1 |
|       2 |    0 |      2 |
|       3 |    0 |      3 |
|       4 |    0 |      4 |
|       5 |    0 |      5 |
|       6 |    0 |      6 |
|       7 |    0 |      7 |
|       8 |    0 |      8 |
|       9 |    0 |      9 |
+---------+------+--------+
10 rows in set (0.00 sec)

mysql> select * from dim_time order by timekey desc limit 10;
+---------+------+--------+
| TimeKey | Hour | Minute |
+---------+------+--------+
|    2359 |   23 |     59 |
|    2358 |   23 |     58 |
|    2357 |   23 |     57 |
|    2356 |   23 |     56 |
|    2355 |   23 |     55 |
|    2354 |   23 |     54 |
|    2353 |   23 |     53 |
|    2352 |   23 |     52 |
|    2351 |   23 |     51 |
|    2350 |   23 |     50 |
+---------+------+--------+
10 rows in set (0.00 sec)

3. 日期循环

3.1 需求

今天需要从订单库中找出过去六个月的订单中是桌面机的订单，所以需要写一个简单的日期循环，用于读取数据。

3.2实现

drop procedure if exists date_loop;

delimiter //
create procedure date_loop()
begin
    declare i int default 1;
	declare start_date date ;  -- 当前日子减去6个月
	declare end_date date ; -- 当前天
	
	select date_sub(current_date(),interval 6 month) into start_date;
	select current_date() into end_date;
	
    while start_date < end_date
    do
        select start_date;
        set start_date = date_add(start_date,interval 1 day);
    end while;
    commit;
end //
delimiter ;

4.参考文章

• https://blog.csdn.net/luogan129/article/details/73691286