mysql - 在 SQL 中将行转换为列

Question

考虑带有架构的表

orders(user int, amount int, created datetime);

一行=一笔交易，我想按用户查询交易数据组

例如

User    First_Order_Amount    First_Order_DateTime Second_OrderAmount    Second_Order_DateTime
1       21                    2019-01-02           22                    2019-01-03
2       13                    2019-01-04           14                    2019-01-05

SQL fiddle :https://www.db-fiddle.com/f/v4gZUMFbuYorB27AH9yBKy/8

Answer 1

如果您使用的是MySQL 8+，您还可以使用窗口函数来代替group by:

SELECT user, amount, created FROM
(SELECT * ,
ROW_NUMBER() OVER (PARTITION BY user ORDER BY user) AS rn
from orders) t
where t.rn = 1