选择是否存在，否则插入? [英] Select if exist else insert?

问题描述

IF EXISTS (select * from users where username = 'something') THEN
    select id from users where username = 'something';
ELSE 
    insert into users (username) values ('something');
END IF;

推荐答案

您的语句就可以了.唯一的问题是，您不能像普通查询一样使用它.像IF或WHILE这样的控制结构只允许在存储过程或函数中使用.

Your statement is fine as it is. Only problem is, you can't use it like a normal query. Control structures like IF or WHILE are only allowed in stored procedures or functions.

只需创建一个像这样的过程:

Just create a procedure like this:

delimiter $$

create procedure select_or_insert()
begin

IF EXISTS (select * from users where username = 'something') THEN
    select id from users where username = 'something';
ELSE 
    insert into users (username) values ('something');
END IF;

end $$

并这样称呼它:

call select_or_insert();

就是这样.

这篇关于选择是否存在，否则插入?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！