SQL在Where语句中使用别名

Question

我怎么能在where语句中使用别名.

示例:

SELECT SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM MyTable
WHERE Col1 = 'MySearch'

我使用MSSQL 2005

Answer 1

您可以使用"having"而不是"where".

SELECT
    SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM
    MyTable
HAVING
    Col1 = 'MySearch'

在执行查询后执行"where".小心在合适的条件下使用它,以避免性能问题.

Answer 2

不可能,但您可以执行以下操作:

SELECT SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM MyTable
WHERE SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3) = 'MySearch'

不需要子查询或黑客攻击

Answer 3

使用子查询:

SELECT * 
FROM 
  (SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3) AS Col1 FROM MyTable)
WHERE Col1 = 'MySearch'

Answer 4

你可以这样做:

SELECT Col1
FROM ( SELECT SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3) AS Col1 ) AS x
WHERE Col1 = 'MySearch'

Answer 5

SELECT * FROM (
  SELECT SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
  FROM MyTable
)
WHERE Col1 = 'MySearch'

(我知道这在Oracle中有效,我相信它是标准的SQL,可以在MSSQL中使用.)