2

在 sqlalchemy 中，我试图合并表，然后使用WHEREandORDER_BY

就像是

SELECT *
FROM (
  SELECT [TABLE_ONE].[SOME_ID] AS [SOME_ID]
  FROM [TABLE_ONE] 
  UNION 
  SELECT [TABLE_TWO].[SOME_ID] AS [SOME_ID]
  FROM [TABLE_TWO]
) AS anon_1
WHERE ...

SQL炼金术：

select_q = select([TABLE_ONE.c.SOME_ID], TABLE_ONE)
select_w = select([TABLE_TWO.c.SOME_ID], TABLE_TWO)
union_qw = union(select_q,select_w) 
union_qw_aliased = aliased(union_qw)
s = select('*',union_qw_aliased)

但 SQLAlchemy 生成 SQL 代码：

SELECT anon_1.[SOME_ID]
FROM (SELECT [TABLE_ONE].[SOME_ID] AS [SOME_ID]
FROM [TABLE_ONE] UNION SELECT [TABLE_TWO].[SOME_ID] AS [SOME_ID]
FROM [TABLE_TWO]) AS anon_1
WHERE SELECT [TABLE_ONE].[SOME_ID]
FROM [TABLE_ONE] UNION SELECT [TABLE_TWO].[SOME_ID]
FROM [TABLE_TWO]

任何帮助表示赞赏

4

1 回答 1

2

您误用了“select()”的第二个参数，它实际上是“whereclause”（尽管我们现在鼓励使用该where()方法）。FROM 子句通常隐含在您选择的列中。对于您的“选择 *”，我们可以使用以下方法设置显式 FROM select_from()：

from sqlalchemy import *

m = MetaData()
t1 = Table('t1', m, Column('id', Integer))
t2 = Table('t2', m, Column('id', Integer))

select_q = select([t1])
select_w = select([t2])
union_qw = union(select_q, select_w)
union_qw_aliased = union_qw.alias()
s = select('*').select_from(union_qw_aliased)

print s

输出：

SELECT * 
FROM (SELECT t1.id AS id 
FROM t1 UNION SELECT t2.id AS id 
FROM t2) AS anon_1

要在 WHERE 上做更多事情，请使用where()并针对 union_qw_aliased 执行此操作：

print s.where(union_qw_aliased.c.id == 5)

输出：

SELECT * 
FROM (SELECT t1.id AS id 
FROM t1 UNION SELECT t2.id AS id 
FROM t2) AS anon_1 
WHERE anon_1.id = :id_1
于 2013-03-12T02:06:55.393 回答