sql-server - SQL Server：如何检查返回字段的值是否不为空

Question

我有如下 SQL 语句：

SELECT  ReturnDate
FROM    <joins>
WHERE   <conditions>

如何检查 ReturnDate 是否不为空？

Answer 1

您可以使用CASE（IS NULL或IS NOT NULL）：

SELECT CASE 
         WHEN ReturnDate IS NULL THEN 'It is null' 
         ELSE 'It is not null' 
       END AS IsItNull 
FROM   dbo.tablename ....

如果您需要过滤NULL/NOT NULL值，您还可以使用IS NOT NULL：

WHERE ReturnDate IS NOT NULL  ...

Answer 2

Check the returnDate with the "Is Null"

Answer 3

如果您不想选择任何为空的记录，请使用以下内容：

SELECT  ReturnDate
FROM    <joins>
WHERE   ReturnDate IS NOT NULL AND <conditions>

Answer 4

Try this query

SELECT  ReturnDate
FROM    joins
WHERE   conditions AND ReturnDate IS NOT NULL;