select from 2 table based on count of 3rd table

Question

I have 3 tables. member reimbursement and receipt. I want to display member's first name,reimbursement total that has a receipt. For example

member

member_id   member_name
1           luffy
2           zoro
3           nami

reimbursement

reimburse_id member_id reimburse_total
1            1         5000
2            2         10000
3            3         10000

receipt

receipt_id  reimburse_id reimburse_price reimburse_no
1            1           2500            2012232
2            1           2500            2012123
3            2           5000            2012454
4            2           5000            2012565

I want to display all reimbursement of the member which has receipt. In this case the select query should return like this

name   No. of reimburse total
luffy         1         5000 
zoro          1         10000
nami          0         0

So far this i what i got

SELECT member.member_name,
       COU­NT(distinct reimbursement.reimbu­rse_id) as nor,
       SUM(distinct reimbursement.reimbu­rse_total)
FROM member INNER JOIN
     reimbursement 
     ON member.member_id = reim­bursement.member_id INNER JOIN
     receipt
     ON reimbursement.reimbu­rse_id=receipt.reimb­urse_id
GROUP BY member.memberID

but i got the wrong total.

Answer 1

Hmmm. This is a little strange because you are only using receipt to determine if the values should be used. One method is LEFT JOIN and some conditional logic:

SELECT m.member_name,
       COUNT(rr.reimburse_id) as nor,
       SUM(CASE WHEN rr.reimburse_id IS NOT NULL THEN reimburse_total ELSE 0 END) as reimbu­rse_total
FROM member m LEFT JOIN
     reimbursement r
     ON m.member_id = r.member_id LEFT JOIN
     (SELECT DISTINCT rr.reimburse_id
      FROM receipt rr
     ) rr
     ON r.reimbu­rse_id = rr.reimb­urse_id
GROUP BY m.memberID, m.member_name;

The logic behind this query is to use the receipt table only to determine if a reimbursement is available. The select distinct removes duplicates. Then the left join and case determine if there are matches to the table.