blocks|key|4598079|text|SELECT+isnull(FIRST,'')+AS+FIRST,+LAST+FROM+CUSTOMER|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4598080|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>SELECT isnull(FIRST,'') AS FIRST, LAST FROM CUSTOMER
</code></pre>

blocks|key|2492962|text|select+isNull(First,'')+from+customer|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2492963|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>select isNull(First,'') from customer
</code></pre>

blocks|key|4598102|text|您还可以使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4598103|SELECT+COALESCE(FIRST,+''),+LAST+FROM+CUSTOMER|code-block|syntax|javascript|4598104|这具有可移植性更好的优点(COALESCE是SQL标准的一部分，而ISNULL不是)|4598105|您还可以使用任意数量的参数，例如|4598106|SELECT+COALESCE(FIRST,+SECOND,+THIRD,+'')...|4598107|和COALESCE将使用遇到的第一个非空值。|4598108|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You can also use

<pre><code>SELECT COALESCE(FIRST, ''), LAST FROM CUSTOMER
</code></pre>

This has the advantage of being more portable (COALESCE is part of the SQL Standard, ISNULL isn't)

You can also use an arbitrary number of arguments, like

<pre><code>SELECT COALESCE(FIRST, SECOND, THIRD, '')...
</code></pre>

And COALESCE will use the first non-null value encountered

blocks|key|2495137|text|SELECT+COALESCE(FIRST,+''),+LAST+FROM+CUSTOMER|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2495138|也行得通|unstyled|2495139|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>SELECT COALESCE(FIRST, ''), LAST FROM CUSTOMER
</code></pre>

would work also

blocks|key|4507869|text|CREATE+FUNCTION+[dbo].[ParamParserFn]
++++(
++++++@delimString+VARCHAR(255)+,
++++++@delim+CHAR(1)
++++)
RETURNS+@paramtable+TABLE
++++(
++++++[Index]+INT+,
++++++[Token]+INT
++++)
AS+
++++BEGIN

++++++++DECLARE+@len+INT+,
++++++++++++@index+INT+,
++++++++++++@nextindex+INT+,
++++++++++++@counter+INT+,
++++++++++++@data+VARCHAR(50)

++++++++SET+@len+=+DATALENGTH(@delimString)
++++++++SET+@index+=+0
++++++++SET+@nextindex+=+0
++++++++SET+@counter+=+0


++++++++WHILE+(+@len+%2B+1+>+@index+)+
++++++++++++BEGIN

++++++++++++++++SET+@nextindex+=+CHARINDEX(@delim,+@delimString,+@index)

++++++++++++++++IF+(+@nextindex+=+0+)+
++++++++++++++++++++SET+@nextindex+=+@len+%2B+1



++++++++++++++++INSERT++@paramtable
++++++++++++++++++++++++SELECT++@counter+,
++++++++++++++++++++++++++++++++SUBSTRING(@delimString,+@index,
++++++++++++++++++++++++++++++++++++++++++@nextindex+-+@index)


++++++++++++++++SELECT++@index+=+@nextindex+%2B+1+,
++++++++++++++++++++++++@counter+=+@counter+%2B+1
++++++++++++END


++++++++RETURN
++++END|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4507870|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>CREATE FUNCTION [dbo].[ParamParserFn]
 (
 @delimString VARCHAR(255) ,
 @delim CHAR(1)
 )
RETURNS @paramtable TABLE
 (
 [Index] INT ,
 [Token] INT
 )
AS 
 BEGIN

 DECLARE @len INT ,
 @index INT ,
 @nextindex INT ,
 @counter INT ,
 @data VARCHAR(50)

 SET @len = DATALENGTH(@delimString)
 SET @index = 0
 SET @nextindex = 0
 SET @counter = 0


 WHILE ( @len + 1 &gt; @index ) 
 BEGIN

 SET @nextindex = CHARINDEX(@delim, @delimString, @index)

 IF ( @nextindex = 0 ) 
 SET @nextindex = @len + 1



 INSERT @paramtable
 SELECT @counter ,
 SUBSTRING(@delimString, @index,
 @nextindex - @index)


 SELECT @index = @nextindex + 1 ,
 @counter = @counter + 1
 END


 RETURN
 END
</code></pre>

I have a nullable varchar and even when it is null, I want my select to return an empty string and not null. That is

<pre><code>SELECT FIRST, LAST 
FROM CUSTOMER
</code></pre>

What I want is if <code>FIRST</code> is null, I want the return to be <code>""</code>

In SQL Server, how to have select return empty string and not null when null

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个可以为空的varchar，即使当它为null时，我也希望我的select返回一个空字符串，而不是null。那是SELECT FIRST, LAST FROM CUSTOMER我想要的是，如果FIRST为null，我希望返回值为""

问在SQL Server中，如何让select在null时返回空字符串和not null
EN

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问在SQL Server中，如何让select在null时返回空字符串和not nullEN