如果条件为“on”的内部联接查询

Question

How to write a query to get the below output (see table no. 4)

table user : role - 1:manager, 2:employee
+----+------+-----------+--------+
| id | name | role      | salary |
+----+------+-----------+--------+
|  1 | a    | 1         |      0 |
|  2 | b    | 1         |      0 |
|  3 | c    | 2         |     10 |
|  4 | d    | 2         |     20 |
|  5 | e    | 2         |     30 |
|  6 | f    | 2         |     40 |
+----+------+-----------+--------+

table city
+----+--------+------+
| id | name   | type |
+----+--------+------+
|  1 | cityA  |    1 |
|  2 | cityB  |    2 |
+----+--------+------+

table user_city_mapping
+----+-----------+---------+
| id | user_id   | city_id |
+----+-----------+---------+
|  1 | 1         | 1       |
|  2 | 2         | 1       |
|  3 | 2         | 2       |
|  4 | 3         | 1       |
|  5 | 4         | 1       |
|  6 | 5         | 2       |
|  7 | 6         | 2       |
+----+-----------+---------+

output required
+------+-------+
| name | total |
+------+-------+
| a    |    30 |
| b    |   100 |
| c    |    10 |
| d    |    20 |
| e    |    70 |
| f    |    70 |
+------+-------+

• user "a", "b", "c", "d" belongs to "cityA" which is of type 1.

• user "b", "e", "f" belong to "cityB" which is of type 2.

• user "c" and "d" falls under manager "a"

• user "c", "d", "e", "f" falls under manager "b"

An explanation for the output required:

1. user "a" gets the total 30 which is the sum of "c" and "d" as both "c" and "d" falls under user "a" manager
2. user "b" gets the total 100 which is the sum of "c", "d", "e" and "f" as all the users fall under user "b" manager
3. user "c" and "d" get the total 10 and 20 which is their own salary and belongs to "cityA" which is of "type 1"
4. user "e" and "f" get the total 70 and 70 which is the sum of the salary of employee belongs to "cityB" which if of "type 2"

In short,
if an employee falls under any manager, the manager get the sum of the salary of the employee under him.
if the employee belongs to "type 1" city he gets his salary.
if an employee belongs to the "type 2" city he gets the sum of all employees belongs to that city.

The above-provided details are the requirement and output. I am not able to get the query for the desired output.

Something which i tried

SELECT b.user_id, sum(salary) 
  FROM user_city_mapping a 
 INNER JOIN user_city_mapping b 
    ON a.city_id = b.city_id 
 INNER JOIN user 
    ON a.user_id = user.id AND role = 2 
 GROUP BY b.user_id

Answer 1

Quite messy and involves parsing the data multiple times. Simplest is to work out the salary by user using a correlated sub query based on city type the total salary for type 2 can be calculated. Working out the salary by city and who manages that city is achieved in the sub query x by first working out a city total and then aggregating by manager The outer query then selects distinct to get rid of duplicate manager rows.

select distinct uname,
         case when salarybyuser = 0 then salarybycity
                else salarybyuser
         end salary
from
(
select u.id uid,u.name uname,ucm.*,c.id cid,
         case when c.type = 1 then salary
              when c.type = 2 and role <> 1 then
              (select sum(salary)
                from user u
                join user_city_mapping ucm on ucm.user_id = u.id
                join city c on c.id = ucm.city_id
                where c.type = 2 and role <> 1
                )
         else 0
         end as salarybyuser,
         x.salarybycity
from user u
join user_city_mapping ucm on ucm.user_id = u.id
join city c on c.id = ucm.city_id
left join
(
select ucm.user_id uid,u.name, sum(SalaryByCity) salarybycity
from   user_city_mapping ucm
join   user u on u.id = ucm.user_id 
join
(
select  c1.id cid,sum(salary) SalaryByCity
from user u1
join user_city_mapping ucm1 on ucm1.user_id = u1.id
join city c1 on c1.id = ucm1.city_id
group by c1.id
) s on s.cid = ucm.city_id
where u.role = 1
group by u.id,u.name
) x on x.uid = u.id
order by c.id,u.role,u.id
) y
order by uid
;




+-------+--------+
| uname | salary |
+-------+--------+
| a     |     30 |
| b     |    100 |
| c     |     10 |
| d     |     20 |
| e     |     70 |
| f     |     70 |
+-------+--------+
6 rows in set (0.002 sec)

Seems messy but this is really 3 queries compressed into 1.