[技巧] Mssql 2000 ,产生随机数注意事项,Case Rand 必须结合 else (5分)

select a = case cast(rand() * 2 as int ) <br>&nbsp; &nbsp; &nbsp; &nbsp;when 0 then 0 <br>&nbsp; &nbsp; &nbsp; &nbsp;when 1 then 1<br>&nbsp; &nbsp; &nbsp; &nbsp;when null then 0<br>&nbsp; &nbsp; &nbsp; &nbsp;else 0<br>&nbsp; &nbsp; &nbsp; &nbsp;end;<br>看上去 cast(rand() * 2 as int ) &nbsp;只能获 0 ,1 <br>&nbsp; &nbsp; 但是 似乎 case cast 搜索的时候 会有超出的情况, 即使使用<br>&nbsp; &nbsp; null 也不行 ,所以必须使用else <br>但是使用<br><br>DECLARE @B FLOAT,@A INT<br>select @b=CAST(rand()*2 AS INT), @a=case <br>WHEN @B = 0 THEN 0<br>WHEN @B = 1 THEN 1<br>WHEN @B = 2 THEN 2<br>when @b is null then 999 END<br>PRINT @B<br>PRINT @A<br><br>确没有这个现象

因为null与null对比不相等<br>when null then 0<br>这句根本不起作用

酱紫