如何编写一个 WHERE 以等于两列同时包含 NULL 值和空值

Question

鉴于我的 table 结构，现在我需要编写一个查询来比较 "STRVAL1 and STRVAL2" 和 "BVAL1 and BVAL2"，如果两者不相同，则应返回该行。

预期结果...

请使用下面的脚本获取数据

DECLARE @TAB TABLE (ID INT, STRVAL1 VARCHAR(8), STRVAL2 VARCHAR(8), BVAL1 BIT, BVAL2 BIT)

    INSERT INTO @TAB VALUES 
      (1, NULL, NULL, NULL, NULL)
    , (2, '', NULL, NULL, NULL)
    , (3, '', '', NULL, NULL)
    , (4, 'VAL', 'VAL', NULL, NULL)
    , (5, 'VAL1', 'VAL2', NULL, NULL)
    , (6, NULL, NULL, 0, NULL)
    , (7, NULL, NULL, 0, 0)
    , (8, NULL, NULL, 1, 1)
    , (9, NULL, NULL, 1, 0)

    SELECT ID, STRVAL1, STRVAL2, BVAL1, BVAL2
    FROM @TAB

Answer 1

您可以只使用比较，尽管 NULL 使这有点麻烦：

select t.*
from @tab t
where ((strval1 <> strval2) or
       (strval1 is null and strval2 is not null) or
       (strval1 is not null and strval2 is null)
      ) or
      ((bval1 <> bval2) or
       (bval1 is null and bval2 is not null) or
       (bval1 is not null and bval2 is null)
      );

Answer 2

您需要组合测试。

select ... from ... where
(strval1 is null and strval2 is not null) or
(strval1 is not null and strval2 is null) or
(strval1 != strval2) or
(bval1 is null and bval2 is not null) or
(bval1 is not null and bval2 is null) or
(bval1 != bval2)

如何编写一个 WHERE 以等于两列同时包含 NULL 值和空值

How to write a WHERE to equate on two columns contains both NULL and empty values

sql

database

sql-server

sql-server-2008-r2

qsqlquery