sql server 中 null + 字符串问题

by Admin6. April 2011 16:27

1.开始定义的字符串都为null.例如:declare @sql

2.字符串加null,结果也为null,例如 select null+' union all ' 结果为null

3.isnull(@sql,'')意思是:当@sql为null时,用字符('')代替.

参考链接：http://www.90qb.com/article/12809131835.html

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