mysql - 计数/组 Null 和 Not Null

Question

我有一个数据库，其中包含 2 个文件，一个日期和一个字符串（还有更多文件，但只有这些文件对此感兴趣），该字符串可以为空。现在我想计算有多少字符串是空的，有多少不是。

SELECT 
  `date`, `serial`, count(`serial`) as count 
FROM 
  `updates` 
WHERE 
  `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59' 
GROUP BY 
  `serial`

这是我目前的代码。我真的不知道如何以一种好的方式汇总它。

问候亚历克斯

// 编辑

结果我想要：

2012-11-25    NULL        2452
2012-11-25    NOT NULL    3476

Answer 1

如果你想计算空字符串，而不是空值，你可以使用这个：

SELECT
  `date`,
  count(`serial`) as count_not_nulls,
  count(case when `serial` is null then 1 end) as count_nulls
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
GROUP BY `date`

编辑：

SELECT `date`, 'NOT NULL', count(`serial`) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
     AND `serial` is not null
GROUP BY `date`
UNION
SELECT `date`, 'NULL', count(1) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
      AND `serial` is null
GROUP BY `date`

Answer 2

简而言之

SELECT 
  DATE( `date` ) the_date, 
  CASE WHEN serial IS NULL THEN 'NULL' ELSE 'NOT NULL' END sernull, 
  COUNT(*)
FROM 
  updates
WHERE
  DATE( `date` ) = '2012-11-25'
GROUP BY 
  the_date, 
  sernull

SQL 小提琴演示

Answer 3

这为您提供序列不为空的计数

SELECT `date`, `serial`, count(`serial`) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59' 
and serial is not null
GROUP BY `serial`

这为您提供序列为空的计数

SELECT `date`, `serial`, count(`serial`) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59' 
and serial is  null
GROUP BY `serial`

Answer 4

希望这对你有帮助。试试这个-

SELECT 'date','serial',count('serial') as count
FROM
(SELECT 'date',
           CASE WHEN 'serial'  is null THEN `NULL'
                   ELSE 'NOT NULL' END as serial
FROM `updates` WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59' )
GROUP BY 'date,'serial'

祝你好运！