Multiple Left Join on same table

Question

I have two table. 1st table => member {member_id, name, active} 2nd table => savings {savings_id, member_id, month, year, amount, type, paid}

Member Table

+-----------+--------+--------+
| member_id | name   | active |
+-----------+--------+--------+
|       105 | Andri  | 1      |
|       106 | Steve  | 1      |
|       110 | Soraya | 1      |
|       111 | Eva    | 1      |
|       112 | Sonia  | 1      |
+-----------+--------+--------+

Savings Table

+------------+-----------+-------+------+--------+------+------+
| savings_id | member_id | month | year | amount | type | paid |
+------------+-----------+-------+------+--------+------+------+
|          1 |       120 |  NULL | NULL | 150000 |    1 | 1    |
|         14 |       105 |     7 | 2014 |  80000 |    2 | 1    |
|         15 |       105 |     7 | 2014 |  25000 |    3 | 1    |
|         16 |       105 |     7 | 2014 |  60000 |    4 | 1    |
|         17 |       105 |     7 | 2014 | 100000 |    5 | 1    |
|         18 |       106 |     7 | 2014 |  80000 |    2 | 1    |
|         19 |       106 |     7 | 2014 |  25000 |    3 | 1    |
|         20 |       106 |     7 | 2014 |  60000 |    4 | 1    |
|         21 |       106 |     7 | 2014 | 100000 |    5 | 1    |
|         31 |       110 |     7 | 2014 |  25000 |    3 | 1    |
|         32 |       110 |     7 | 2014 |  60000 |    4 | 1    |
|         33 |       110 |     7 | 2014 | 100000 |    5 | 1    |
|         34 |       111 |     7 | 2014 |  80000 |    2 | 1    |
|         35 |       111 |     7 | 2014 |  25000 |    3 | 1    |
|         36 |       111 |     7 | 2014 |  60000 |    4 | 1    |
|         37 |       111 |     7 | 2014 | 100000 |    5 | 1    |
|         38 |       112 |     7 | 2014 |  80000 |    2 | 1    |
|         39 |       112 |     7 | 2014 |  25000 |    3 | 1    |
|         40 |       112 |     7 | 2014 |  60000 |    4 | 1    |
|         41 |       112 |     7 | 2014 | 100000 |    5 | 1    |
|         85 |       105 |     7 | 2015 |  80000 |    2 | 1    |
|         86 |       105 |     7 | 2015 |  25000 |    3 | 1    |
|         87 |       105 |     7 | 2015 |  60000 |    4 | 1    |
|         88 |       105 |     7 | 2015 | 100000 |    5 | 1    |
|         89 |       106 |     7 | 2015 |  80000 |    2 |      |
|         90 |       106 |     7 | 2015 |  25000 |    3 |      |
|         91 |       106 |     7 | 2015 |  60000 |    4 |      |
|         92 |       106 |     7 | 2015 | 100000 |    5 |      |
|        101 |       110 |     7 | 2015 |  80000 |    2 |      |
|        102 |       110 |     7 | 2015 |  25000 |    3 |      |
|        103 |       110 |     7 | 2015 |  60000 |    4 |      |
|        104 |       110 |     7 | 2015 | 100000 |    5 |      |
|        105 |       111 |     7 | 2015 |  80000 |    2 | 1    |
|        106 |       111 |     7 | 2015 |  25000 |    3 | 1    |
|        107 |       111 |     7 | 2015 |  60000 |    4 | 1    |
|        108 |       111 |     7 | 2015 | 100000 |    5 | 1    |
|        109 |       112 |     7 | 2015 |  80000 |    2 |      |
|        110 |       112 |     7 | 2015 |  25000 |    3 |      |
|        111 |       112 |     7 | 2015 |  60000 |    4 |      |
|        144 |       110 |     7 | 2014 |  50000 |    1 | 1    |
+------------+-----------+-------+------+--------+------+------+

When member make a savings, they could choose 5 type of savings, What i want to do is to make a list of member and all of their saving.

This is mysql query

SELECT m.member_id, name, 
SUM(s1.amount) as savings1,
SUM(s2.amount) as savings2,
SUM(s3.amount) as savings3,
SUM(s4.amount) as savings4,
SUM(s5.amount) as savings5
FROM members m
LEFT JOIN savings s1 ON s1.member_id = m.member_id AND s1.type = 1 AND s1.paid = 1
LEFT JOIN savings s2 ON s2.member_id = m.member_id AND s2.type = 2 AND s2.paid = 1
LEFT JOIN savings s3 ON s3.member_id = m.member_id AND s3.type = 3 AND s3.paid = 1
LEFT JOIN savings s4 ON s4.member_id = m.member_id AND s4.type = 4 AND s4.paid = 1
LEFT JOIN savings s5 ON s5.member_id = m.member_id AND s5.type = 5 AND s5.paid = 1
WHERE 
active = 1
GROUP BY m.member_id

This is the output

+-----------+--------+----------+----------+----------+----------+----------+
| member_id | name   | savings1 | savings2 | savings3 | savings4 | savings5 |
+-----------+--------+----------+----------+----------+----------+----------+
|       105 | Andri  |     NULL |  1280000 |   400000 |   960000 |  1600000 |
|       106 | Steve  |     NULL |    80000 |    25000 |    60000 |   100000 |
|       110 | Soraya |    50000 |     NULL |    25000 |    60000 |   100000 |
|       111 | Eva    |     NULL |  1280000 |   400000 |   960000 |  1600000 |
|       112 | Sonia  |     NULL |    80000 |    25000 |    60000 |   100000 |
+-----------+--------+----------+----------+----------+----------+----------+

As you can see the calculation is not right, for example savings2 for member 105 it should be 160K. Any suggestion what should be the query for this case.

http://sqlfiddle.com/#!2/9eca9/1

Answer 1

The problem is you're forming the full join product before summation. So if there is more than one row in more than one of your savings tables you will end up with duplication. If you perform the join without summation, you can clearly see what is going on. There are two ways around this.

1. Do all summations in derived tables:

   SELECT m.member_id, name, 
   s1.amount as savings1,
   s2.amount as savings2,
   ...
   FROM members m
   LEFT JOIN (
       select SUM(amount) as amount, member_id
       from savings
       where type = 1 and paid = 1
       group by member_id
   ) s1 ON s1.member_id = m.member_id
   LEFT JOIN (
       select SUM(amount) as amount, member_id
       from savings
       where type = 2 and paid = 1
       group by member_id
   ) s2 ON s2.member_id = m.member_id
   ...
   WHERE active = 1
   GROUP BY m.member_id
   

2. Join once and use a conditional sum:

   SELECT m.member_id, name, 
       SUM(CASE WHEN s.type = 1 then s.amount ELSE NULL END) as savings1,
       SUM(CASE WHEN s.type = 2 then s.amount ELSE NULL END) as savings2,
       ...
   LEFT JOIN savings s s2 ON s.member_id = m.member_id AND s.paid = 1
   WHERE active = 1
   GROUP BY m.member_id
   

Answer 2

You probably do not need multiple left joins and could be done as

SELECT 
m.member_id,
m.name,
SUM(case when s.type= 1 then s.amount end) as savings1,
SUM(case when s.type= 2 then s.amount end) as savings2,
SUM(case when s.type= 3 then s.amount end) as savings3,
SUM(case when s.type= 4 then s.amount end) as savings4,
SUM(case when s.type= 5 then s.amount end) as savings5
FROM savings s
join members m on m.member_id = s.member_id
WHERE 
m.active = 1
GROUP BY m.member_id

Answer 3

this should work

SELECT m.member_id, name, 

sum((case when s1.type=1 then s1.amount end)) as savings1,

sum((case when s1.type=2 then s1.amount end)) as savings2,

sum((case when s1.type=3 then s1.amount end)) as savings3,

sum((case when s1.type=4 then s1.amount end)) as savings4,

sum((case when s1.type=5 then s1.amount end)) as savings5

FROM members m

LEFT JOIN savings s1 ON s1.member_id = m.member_id 

WHERE active = 1 and s1.paid=1

GROUP BY m.member_id