Question

当我不使用WHERE子句时，查询工作正常。如何使其与WHERE子句一起使用？这太雄心勃勃了吗？

由于

错误：

[Err] 1054 - Unknown column 'claims.client_name' in 'where clause'

SQL：

SELECT
(
    CASE
        WHEN client = 'Driver' THEN (SELECT fullname FROM driver WHERE id = claims.client_id)
        WHEN client = 'Passenger' THEN (SELECT fullname FROM passengers WHERE id = claims.client_id)
        WHEN client = 'Thirdparty' THEN (SELECT fullname FROM thirdparty WHERE id = claims.client_id)
        WHEN client = '' THEN  NULL
    END
) AS client_name

FROM claims

WHERE (client_name LIKE '%john%')

Answer 1

替换

WHERE (client_name LIKE '%john%')

与

HAVING (client_name LIKE '%john%')

Answer 2

试试这个： -

SELECT  CASE WHEN client = 'Driver' THEN (SELECT fullname FROM driver WHERE id = claims.client_id)
        WHEN client = 'Passenger' THEN (SELECT fullname FROM passengers WHERE id = claims.client_id)
        WHEN client = 'Thirdparty' THEN (SELECT fullname FROM thirdparty WHERE id = claims.client_id)
        WHEN client = '' THEN  NULL
        END AS client_name FROM claims WHERE client_name LIKE '%john%'

希望它会对你有所帮助。

Answer 3

您不能在where子句中使用别名。通常，您会重复给出别名的代码并将其放入。

即，而不是放"WHERE client_name LIKE '%john%'"你可以尝试：

WHERE (CASE
         WHEN client = 'Driver' THEN (SELECT fullname FROM driver WHERE id =
         claims.client_id)
         WHEN client = 'Passenger' THEN (SELECT fullname FROM passengers WHERE id = 
         claims.client_id)
         WHEN client = 'Thirdparty' THEN (SELECT fullname FROM thirdparty WHERE id =
         claims.client_id)
         WHEN client = '' THEN  NULL 
       END) LIKE '%john%'

我还没有在开发工具中试过这个，所以它可能需要一些抛光。

Answer 4

您不能在WHERE子句中直接使用别名。检查答案HERE。遗憾的是，您无法使用SQL Server中可用的CTE，而是可以使用
临时表。

尝试以下声明

SELECT tmp.* FROM
(
   SELECT CASE
        WHEN client = 'Driver' THEN (SELECT fullname FROM driver WHERE id = claims.client_id)
        WHEN client = 'Passenger' THEN (SELECT fullname FROM passengers WHERE id = claims.client_id)
        WHEN client = 'Thirdparty' THEN (SELECT fullname FROM thirdparty WHERE id = claims.client_id)
        WHEN client = '' THEN  NULL
    END AS client_name FROM claims
) AS tmp
WHERE tmp.client_name LIKE '%john%'

WHERE子句从AS的一部分中进行选择

4 个答案: