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  • mysql数据库之函数、流程控制

    函数

    注意与存储过程的区别,mysql内置的函数只能在sql语句中使用!

    参考博客:http://www.cnblogs.com/linhaifeng/articles/7495918.html#_label2

    CREATE TABLE blog (
        id INT PRIMARY KEY auto_increment,
        NAME CHAR (32),
        sub_time datetime
    );
    ​
    INSERT INTO blog (NAME, sub_time)
    VALUES
        ('第1篇','2015-03-01 11:31:21'),
        ('第2篇','2015-03-11 16:31:21'),
        ('第3篇','2016-07-01 10:21:31'),
        ('第4篇','2016-07-22 09:23:21'),
        ('第5篇','2016-07-23 10:11:11'),
        ('第6篇','2016-07-25 11:21:31'),
        ('第7篇','2017-03-01 15:33:21'),
        ('第8篇','2017-03-01 17:32:21'),
        ('第9篇','2017-03-01 18:31:21');
    ​
    select date_format(sub_time,'%Y-%m'),count(id) from blog group by date_format(sub_time,'%Y-%m');

    # 查询结果:

    +-------------------------------+-----------+
    | date_format(sub_time,"%Y-%m") | count(id) |
    +-------------------------------+-----------+
    | 2015-03 | 2 |
    | 2016-07 | 4 |
    | 2017-03 | 3 |
    +-------------------------------+-----------+

     

    流程控制

    # if条件语句
    delimiter //
    CREATE PROCEDURE proc_if ()
    BEGIN
        
        declare i int default 0;
        if i = 1 THEN
            SELECT 1;
        ELSEIF i = 2 THEN
            SELECT 2;
        ELSE
            SELECT 7;
        END IF;
    ​
    END //
    delimiter ;
    # while循环
    delimiter //
    CREATE PROCEDURE proc_while ()
    BEGINDECLARE num INT ;
        SET num = 0 ;
        WHILE num < 10 DO
            SELECT
                num ;
            SET num = num + 1 ;
        END WHILE ;
    ​
    END //
    delimiter ;

     

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  • 原文地址:https://www.cnblogs.com/dongxixi/p/10885297.html
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