MYSQL CASE THEN语句具有多个值 [英] MYSQL CASE THEN statement with multiple values

问题描述

我正在尝试使用CASE语句选择多个值.我注意到我们不能做

I am trying go select multiple values with CASE statement. I noticed we cannot do

CASE 
    WHEN wall.type="bk" 
    THEN books.id1,books.id2, // and so on
END as column_1,

是否有一种方法可以对多列执行THEN还是只需要编写一堆CASE THEN语句?看起来很乱

Is there a way to do THEN with multiple columns or do we need to simply write a bunch of CASE THEN statements? that seems messy

推荐答案

不，它只是一个值.另外，使用多列"并将这些多列命名为column_1是矛盾的，对吗? :)

No, it is just a single value. Additionally, it is contradictory to use "multiple columns" and name those multiple columns as column_1, right? :)

您可以使用另一列来存储另一个ID(具有类似的情况)，并使用空值来表示else值，就像您现在所做的那样.

You can use another column to store the other id with (a similar case) and use nulls to represent the else values, just like you're doing now.

示例:

CASE 
    WHEN wall.type="bk" 
    THEN books.id1
END as column_1,
CASE 
    WHEN wall.type="bk" 
    THEN books.id2
END as column_2

查看官方文档以获取更多信息.

Check the official documentation for more information.

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