SQL-计入多列 [英] Sql - count into multiple columns

问题描述

我有一个这样的表:

 num | type
-----+------
 123 | 3
 123 | 2
 123 | 3
 123 | 2
 124 | 3
 124 | 1
 124 | 3
 124 | 3

我想按num列分组，并有一个列计算每种不同的类型(我事先知道这里所有可能的值).所以我会得到:

I want to group by the num column, and have a column counting each distinct type (I know all the possible values here in advance). So I would get:

 num | 1 | 2 | 3
-----+---+---+---
 123 | 0 | 2 | 2
 124 | 1 | 0 | 3

SQL可能吗?我正在使用MySql.

Is this possible with SQL? I am using MySql.

推荐答案

SELECT `num`,
    SUM(type = 1) as `1`, 
    SUM(type = 2) as `2`, 
    SUM(type = 3) as `3`
FROM `your_table`
GROUP BY `num`

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