Question

我有以下SQL查询：

SELECT jobs.ID,  jobs.title,
SUM(CASE WHEN jobresponses.result = 'true' THEN 1 ELSE 0 END) as True,
SUM(CASE WHEN jobresponses.result = 'false' THEN 1 ELSE 0 END) as False,
SUM(CASE WHEN jobresponses.result != 'true' AND jobresponses.result != 'false' THEN 1 ELSE 0 END) as Incomplete
FROM jobresponses 
JOIN jobs on jobresponses.jobId = jobs.ID
WHERE jobs.ID = 1
GROUP BY jobs.ID, jobs.title

第三种情况表达式实际上使用result NULL来计算值，但要安全（''，undefined和NULL之间）我想基本上抓住所有“其他”类型字段。但是，问题是不计算NULL值。请参阅this SQL小提琴。

Answer 1

使用IS NULL：

SELECT jobs.ID,  jobs.title,
SUM(CASE WHEN jobresponses.result = 'true' THEN 1 ELSE 0 END) as True,
SUM(CASE WHEN jobresponses.result = 'false' THEN 1 ELSE 0 END) as False,
SUM(CASE WHEN jobresponses.result IS NULL                      -- detect NULL
              OR jobresponses.result NOT IN ('true', 'false')  -- other values
   THEN 1 ELSE 0 END) as Incomplete
FROM jobresponses 
JOIN jobs on jobresponses.jobId = jobs.ID
WHERE jobs.ID = 1
GROUP BY jobs.ID, jobs.title;

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Answer 2

NULL = NULL评估为NULL，这既不是真也不是假。如果您想要抓住任何不是'true'或'false'的内容，那么您可以使用

SUM(CASE WHEN (jobresponses.result = 'true' OR jobresponses.result = 'false') THEN 0 ELSE 1 END) as Incomplete

Answer 3

这样做的一种简单方法可以反转then / else逻辑：

SELECT j.ID,  j.title,
       SUM(CASE WHEN jr.result = 'true' THEN 1 ELSE 0 END) as True,
       SUM(CASE WHEN jr.result = 'false' THEN 1 ELSE 0 END) as False,
       SUM(CASE WHEN jr.result IN ('true', 'false') THEN 0 ELSE 1 END) as Incomplete
FROM jobresponses jr JOIN
     jobs j
     ON jr.jobId = j.ID
WHERE j.ID = 1;
GROUP BY j.ID, j.title

Answer 4

您可以查询如下：

SELECT jobs.ID,  jobs.title,
SUM(CASE WHEN jobresponses.result = 'true' THEN 1 ELSE 0 END) as True,
SUM(CASE WHEN jobresponses.result = 'false' THEN 1 ELSE 0 END) as False,
SUM(CASE WHEN jobresponses.result is null or ltrim(rtrim(jobresponses)) = '' THEN 1 ELSE 0 END) as Incomplete
FROM jobresponses 
JOIN jobs on jobresponses.jobId = jobs.ID
WHERE jobs.ID = 1
GROUP BY jobs.ID, jobs.title

Answer 5

不要使用ISNULL（）。它会工作，但它是一个T-SQL函数。请改用COALESCE（）。它是多平台的。

SUM(CASE WHEN COALESCE(jobresponses.result,'') = 'true' THEN 1 ELSE 0 END) as True,
SUM(CASE WHEN COALESCE(jobresponses.result,'') = 'false' THEN 1 ELSE 0 END) as False,
SUM(CASE WHEN COALESCE(jobresponses.result,'') NOT IN ('true','false') THEN 1 ELSE 0 END) as Incomplete

此外，jobresponses.result的唯一有效值应该是＆＃39; true＆＃39;，＆＃39; false＆＃39;还是null？如果是这样，您最好将该字段设为bit/Boolean而不是varchar()。它将显着降低存储要求，并且使用起来更容易，更有效。

在case语句中计算NULL值

5 个答案: