Question

我使用sqlaclhemy查詢我的數據庫在我的Python項目，我是相當新的SQLAlchemy的，但像此刻的概念，我在做很簡單的事情一樣，

sel = select([staff.c.name]) \ 
    .select_from(staff) \ 
    .where(staff.c.workbase != "") \ 
    .where((staff.c.status != 'Left') & (staff.c.status != 'Name Changed')) 

我的項目

部分需要更復雜的SQL查詢，但我要保持它在SQLAlchemy中，我的原始的SQL看起來像這樣，

SELECT A.a_allowance, B.b_allowance, C.c_allowance, A.name, A.leave_allowance 
FROM 
    (SELECT ROUND(leave_allowance * 0.32, 2) as a_allowance, name, leave_allowance FROM staff_list) A 
    INNER JOIN 
    (SELECT ROUND(leave_allowance * 0.40, 2) as b_allowance, name FROM staff_list) B 
    ON A.name = B.name 
    INNER JOIN 
    (SELECT ROUND(leave_allowance * 0.28, 2) as c_allowance, name FROM staff_list) C 
    ON A.name = C.name 
    WHERE A.name = 'Jones Jones'; 

我不知道該怎麼辦嵌套選擇等，在SQLAlchemy的。

Answer 1

你就可以生產使用.join()加入：

>>> print(foo.join(bar, foo.c.bar_id == bar.c.id)) 
foo JOIN bar ON foo.bar_id = bar.id 

您可以通過子查詢代替表達式中的表名：

>>> left = select([foo.c.bar_id]).select_from(foo).where(foo.c.baz > 0).alias("left") 
>>> print(left.join(bar, left.c.bar_id == bar.c.id)) 
(SELECT foo.bar_id AS bar_id 
FROM foo 
WHERE foo.baz > :baz_1) AS "left" JOIN bar ON "left".bar_id = bar.id 

在大多數情況下，子查詢行爲酷似表。