Mysql 从单列中选择计数值 [英] Mysql select count values from a single column

问题描述

A 有一列名为 key - 1,1,2,2,2,2,3现在我用 3 个查询来做:

A have a column named key - 1,1,2,2,2,2,3 Now i do it with 3 querys:

SELECT count(key) as k FROM `test` WHERE key=1
SELECT count(key) as k FROM `test` WHERE key=2
SELECT count(key) as k FROM `test` WHERE key=3

如何在一次查询中计算出有多少个 1、2、3?

How to count in one query how many 1,2,3?

推荐答案

Use group by:

Use group by:

SELECT `key`, COUNT(*) FROM `test` GROUP BY `key`;

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