日期:2014-05-18 浏览次数:20615 次
declare @alive bit; set @alive = null; if @alive = 1 or @alive != 1 print 'Alive or Dead'; else print 'Huh? Neither alive nor dead'; if @alive=@alive PRINT 'It must equal itself, right?' ELSE PRINT 'Not always. null does not equal null';
declare @alive bit; set @alive = null; if @alive = 1 or @alive != 1 print 'Alive or Dead'; else print 'Huh? Neither alive nor dead'; if null is null PRINT 'It must equal itself, right?' ELSE PRINT 'Not always. null does not equal null'; /* Huh? Neither alive nor dead It must equal itself, right?
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Null is woman's looks
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null does not equal null
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What would be the output ? declare @a smallint set @a = 0 select nullif ( @a , '' )
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NULL<>''
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mark
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null does not equal null!
null is null!
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俺只会中文
NULL确实不能比较只能IS
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改了配置已经可以比较哦
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都是些外国人。呵呵 null是什么都没有的意思。所以由此所得 null就不是数字
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is null
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其实楼主是拉晒英文呢
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null=undefined value=未知
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set ansi_nulls off后结果就不同了.
set ansi_nulls off declare @alive bit; set @alive = null; if @alive = 1 or @alive != 1 print 'Alive or Dead'; else print 'Huh? Neither alive nor dead'; if @alive=@alive PRINT 'It must equal itself, right?' ELSE PRINT 'Not always. null does not equal null'; --> 结果 Alive or Dead It must equal itself, right?
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null确实不能比较 但是可以通过 isnull转化在比较 isnull(字段,'') 如果是NULL则转化为 ‘’ 空字符串
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