在mysql的存储过程中使用条件（关键字'IF'等）形成查询

Posted 2023-02-24

【中文标题】在mysql的存储过程中使用条件（关键字\'IF\'等）形成查询

【英文标题】：use conditions (keyword 'IF' etc) in the formation of queries in stored procedures in mysql在mysql的存储过程中使用条件（关键字'IF'等）形成查询

【发布时间】：2017-01-29 15:06:57

【问题描述】：

我写了一个存储过程（mysql，我的第一步）：

PROCEDURE `get_SiteAttendanceByPages`(IN _UserName VARCHAR(20) CHARSET utf8, IN _DateS BIGINT(20), IN _DateF BIGINT(20))
BEGIN

    IF _UserName = '' THEN
        SELECT 
            login_history.event_id, 
            COUNT(login_history.event_id) AS count 
        FROM 
            login_history 
        INNER JOIN 
            client_pages
        ON 
            login_history.event_id = client_pages.id
        WHERE 
            (login_history.time_stamp BETWEEN _DateS AND _DateF) AND client_pages.name LIKE '%[p]%'
        GROUP BY 
            login_history.event_id
        ORDER BY 
            client_pages.name;

    ELSE
        SELECT 
            login_history.event_id, 
            COUNT(login_history.event_id) AS count 
        FROM 
            login_history 
        INNER JOIN 
            client_pages
        ON 
            login_history.event_id = client_pages.id
        WHERE 
            login_history.user_name = _UserName AND (login_history.time_stamp BETWEEN _DateS AND _DateF) AND client_pages.name LIKE '%[p]%'
        GROUP BY 
            login_history.event_id
        ORDER BY 
            client_pages.name;

    END IF;

END

事实上，我想编写更短的代码。为此，您只需更改从表中制作样本的条件。

是否可以实现mysql存储过程？ 那些。做这样的事情：

        WHERE 
            (_UserName == '') ? ('') : ('login_history.user_name = _UserName AND') (login_history.time_stamp BETWEEN _DateS AND _DateF) AND client_pages.name LIKE '%[p]%'

?

【问题讨论】：

在 mysql 中的 Store 过程或函数或触发器上尚不支持带有三元运算符的速记 if-else。

【参考方案1】：

解决方案

SELECT 
    login_history.event_id, 
    COUNT(login_history.event_id) AS count 
FROM 
    login_history 
INNER JOIN 
    client_pages
ON 
    login_history.event_id = client_pages.id
WHERE 
    ((_UserName <> '' AND login_history.user_name = _UserName) OR _UserName = '') AND  (login_history.time_stamp BETWEEN _DateS AND _DateF) AND client_pages.name LIKE '%[p]%'
GROUP BY 
    login_history.event_id
ORDER BY 
    client_pages.name;