SQL循环语句

前言

有时咱们须要增加很多测试的数据 在不应用Java的状况下 如何用SQL语句进行增加 ? 本文将讲述单层循环，双层循环，以及日期循环

单层循环

测试表代码

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

再编写存储过程，其中波及到循环的应用。咱们欲通过这个存储过程，来达到往表中插入数据的成果

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

上面是输入后果:

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 | bookworm1     ||           2 | bookworm2     ||           3 | bookworm3     ||           4 | bookworm4     ||           5 | bookworm5     ||           6 | bookworm6     ||           7 | bookworm7     ||           8 | bookworm8     ||           9 | bookworm9     |+-------------+---------------+9 rows in set (0.00 sec)

drop procedure if exists insert_while：如果存在函数insertwhile先删除它

delimiter //：将结束符定义为//在begin和end中会应用;如果不换程序会谬误

create procedure：创立存储过程

delimiter ;结束符换回;号

双重循环

创立表

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

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

后果

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)

日期循环

3.1 需要
明天须要从订单库中找出过来六个月的订单，所以须要写一个简略的日期循环，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 ;  -- 以后日子减去6个月    declare end_date date ; -- 以后天        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 ;

date_sub(object,interval):从指定日期减去指定年，月，日，时，分，秒

object:

• 必须
• 规定一个由data_current()返回的DataTime的对象

interval:

• 必须
• 规定是一个interval对象

返回值:如果胜利返回DataTime对象,如果失败返回false

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