MySQL中的COUNT CASE和WHEN语句 [英] COUNT CASE and WHEN statement in MySQL

问题描述

如何在MySQL查询中使用COUNT CASE和WHEN语句来计算一个MySQL查询中的数据何时为NULL和何时为非NULL?

How to use COUNT CASE and WHEN statement in MySQL query, to count when data is NULL and when it is not NULL in one MySQL query?

推荐答案

使用:

SELECT SUM(CASE 
             WHEN t.your_column IS NULL THEN 1
             ELSE 0
           END) AS numNull,
       SUM(CASE 
             WHEN t.your_column IS NOT NULL THEN 1
             ELSE 0
           END) AS numNotNull
  FROM YOUR_TABLE t

这将汇总NULL&列.整个表都不能为NULL.根据需要，您可能需要GROUP BY子句.

That will sum up the column NULL & not NULL for the entire table. It's likely you need a GROUP BY clause, depending on needs.

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