Question

如果没有记录或0为空，我想返回Column1。

select @var =  Column1
from myschema.mytable
where Id = @suppliedId;

select isnull(@var, 0);

如果0为空，则上述代码会输出Column1。或者如果找不到行

虽然我试图保存一些按键，但结果却是，

select isnull(Column1, 0)
from myschema.mytable 
where Id = @suppliedId;

如果null为空或没有行，则上述代码输出Column1

这里有什么问题吗？或者有没有更短的方式来编写第一个代码？

Answer 1

You can do

SELECT @var = ISNULL(MAX(Column1), 0)
FROM   myschema.mytable
WHERE  Id = @suppliedId;

A scalar aggregate always returns a single row even if the underlying query returns zero rows.

Answer 2

没有真正保存击键，但这样的事情可能会有所帮助： - ）

SELECT TOP 1 tbl.field
FROM
(
    SELECT 0 AS inx, 'no record' AS field
    --if only one row is possible, than set '1' literally
    UNION SELECT ROW_NUMBER() OVER(ORDER BY mytable.orderfield), ISNULL(mytable.Land,'is null')
    FROM mytable
    WHERE IDENTITY = @suppliedID
    ) AS tbl
ORDER BY tbl.inx DESC

如果值返回值。如果记录不存在或列为null，则在Sql Server中以不同的方式返回0

2 个答案: