#按用戶名摸糊查詢
trans_details.query.join(Uses).filter(Users.username.like('%xx%'))
#select xxx from trans_details inner join trans_details on users.id=trans_details.user_id where users.username like '%xx%'
#左外聯接(left join)
trans_details.query.outerjoin(Uses).filter(Users.username.like('%xx%'))
#select xxx from trans_details left outer join trans_details on users.id=trans_details.user_id where users.username like '%xx%'
#以上是已經設置好外鍵,它自動找到關聯的字段.也可以自己指定:
trans_details.query.join(Uses,trans_details.user_id==Users.id).filter(Users.username.like('%xx%'))
#select xxx from trans_details inner join trans_details on users.id=trans_details.user_id where users.username like '%xx%'
#另外一個更復雜的例子:
q=db.session.query(Credit_bills_details.no,Credit_bills_details.amount,Cards.no).outerjoin(Card_trans_details,
Credit_bills_details.no==Card_trans_details.trans_no).join(Cards,Card_trans_details.to_card_id==Cards.id)\
.filter(Credit_bills_details.credit_bill_id==3)
#SELECT credit_bills_details.no AS credit_bills_details_no, credit_bills_details.amount AS credit_bills_details_amount, cards.no AS cards_no
# FROM credit_bills_details LEFT OUTER JOIN card_trans_details ON credit_bills_details.no = card_trans_details.trans_no INNER JOIN cards
# ON card_trans_details.to_card_id = cards.id WHERE credit_bills_details.credit_bill_id = %s
附錄：
SQl內，外，左，右，全連接
表結構：
student
| no |
name |
| 1 |
a |
| 2 |
b |
| 3 |
c |
| 4 |
d |
grade
| no |
grade |
| 1 |
90 |
| 2 |
80 |
| 3 |
85 |
| 3 |
95 |
運行語句如下
select * from student,grade WHERE student.no = grade.no ---普通的where語句
select * from student inner join grade on student.no = grade.no ---內連接語句
select * from student left join grade on student.no = grade.no ---左連接語句
select * from student right join grade on student.no = grade.no ---右連接語句
select * from student full join grade on student.no = grade.no ---全連接語句
運行結果如下：
普通的where語句
no name no grade
1 a 1 90
2 b 2 80
3 c 3 85
3 c 3 90
內連接語句
no name no grade
1 a 1 90
2 b 2 80
3 c 3 85
3 c 3 90
左連接語句
no name no grade
1 a 1 90
2 b 2 80
3 c 3 85
3 c 3 90
4 d NULL NULL
右連接語句
no name no grade
1 a 1 90
2 b 2 80
3 c 3 85
3 c 3 90
全連接語句
no name no grade
1 a 1 90
2 b 2 80
3 c 3 85
3 c 3 90
4 d NULL NULL
總結：
從上面例子可以看出：
內連接和我們平時所用的where語句效果一致，即兩個表的共同的部分
外連接包括（左連接、右連接)
左連接，即已左邊的表為主表，右邊的表為副表，將主表中需要的字段全部列出，然后將副表中的數據按照查詢條件與其對應起來，
右連接則相反。
全連接，則是將兩個表的需要的字段的數據全排列。