如何在MySQL中使用带有pivot的group？

Question

任何人都可以帮我分组2张桌子并显示如下......

我的第一张表是：

user_id | department
-----------------------
1       | user1
----------------------
2       | user2
----------------------

和表2是：

reserve_id | user_id | reserve_status
--------------------------------------
    1      |     1   |        1
--------------------------------------
    2      |     1   |        1
--------------------------------------
    3      |     1   |        2
--------------------------------------
    4      |     2   |        2
--------------------------------------
    5      |     2   |        0
--------------------------------------
    6      |     2   |        1

*reserve_status 0 uncheck, 1 = approve , 2 = disapproval

我想要这样的产品：

department | sumreserve | sumreservapprove | sumreserveunapprove | uncheck
----------------------------------------------------------------------------
 user1     |     3      |        2         |         1           |    0
----------------------------------------------------------------------------
 user2     |     3      |        1         |         1           |    1

抱歉英语不好

Answer 1

您需要透视解决方案。

<强>演示：
假设so_q27895250_users和so_q27895250_reserve为表名

mysql>
mysql> select u.department, count(r.reserve_status) as total_reserves,
    ->     count( case when r.reserve_status = 0
    ->                         then r.reserve_status else null end ) as unchecked,
    ->     count( case when r.reserve_status = 1
    ->                         then r.reserve_status else null end ) as approved,
    ->     count( case when r.reserve_status = 2
    ->                         then r.reserve_status else null end ) as unapproved
    ->   from so_q27895250_reserve r
    ->     left join so_q27895250_users u
    ->                    on r.user_id = u.user_id
    ->  group by r.user_id
    -> ;
+------------+----------------+-----------+----------+------------+
| department | total_reserves | unchecked | approved | unapproved |
+------------+----------------+-----------+----------+------------+
| user1      |              3 |         0 |        2 |          1 |
| user2      |              3 |         1 |        1 |          1 |
+------------+----------------+-----------+----------+------------+
2 rows in set (0.00 sec)