SQL Server在不同列上选择

Question

我想根据SQL Server中的不同列选择一个值，

说

Result = Isnull(A.OUT1,'')<>'' then select A.OUT1
         Isnull(A.OUT2,'')<>'' then select A.OUT2
         Isnull(A.OUT3,'')<>'' then select A.OUT3

如何形成查询以获得结果？

Answer 1

你的意思是这样的：

SELECT CASE 
         WHEN isnull(a.out1,'')  '' THEN a.out1
         WHEN isnull(a.out2,'')  '' THEN a.out2
         WHEN isnull(a.out3,'')  '' THEN a.out3
         ELSE ''
       END AS out_column
FROM the_table a