Mysql查询加入5个表

Question

I am trying to join 5 tables in which i want to get different currency mentioned on different tables against same contract id.
It is giving me results when i join any three tables but when I add one more table in query the server gets unresponsive until I have to kill the process.

Please help me where I am doing a mistake.

SELECT c.department_id,
  c.contract_id,
  c.seller_id,
  c.buyer_id,
  c.contract_ratecurrency AS contractcurrency,
  b.currency_id           AS billcurrency,
  s.saleinv_currency      AS saleinvcurrency,
  cm.currency_id          AS commissioncurrency,
  sl.currency_id          AS cmlogcurrency,
  c.contract_iscancel
FROM tbl_contracts C
JOIN tbl_contract_bill b ON c.contract_id=b.contract_id
JOIN tbl_contract_saleinvoice s ON c.contract_id =s.contract_id
JOIN tbl_commission_payment cm ON c.department_id = cm.department_id
JOIN tbl_saleinvoice_commission_log sl ON c.department_id = sl.department_id
WHERE (c.contract_ratecurrency <> s.saleinv_currency
       OR c.contract_ratecurrency     <> b.currency_id
       OR s.saleinv_currency          <> b.currency_id
       OR cm.currency_id              <> sl.currency_id
       OR c.contract_ratecurrency     <> cm.currency_id
       OR s.saleinv_currency          <> cm.currency_id
       OR b.currency_id               <> cm.currency_id)
AND (c.contract_iscancel        =0)

requried result should be

ccontractid,csellerid,cbuyerid,ccurrency,bcurrency,scurrency,cmcurrency,slcurrency
101,25,50,1,1,2,3,1
102,28,16,2,3,1,3,2

Answer 1

It looks like you are having performance issues. To optimize your database structure you have multiple options:

1. Adding indexes on your keys.

   Let's take a look to your join statement:

   JOIN tbl_saleinvoice_commission_log sl ON c.department_id = sl.department_id

   Adding a clustered index on department_id on tbl_saleinvoice_commission_log table will help you a lot in performance wise. For more information you can check this link.

2. Partitioning is another way to increase performance, but you need to check your database structure to see whether it works for you or not. For more information you can check this link.

Also I believe your tables are one to many, so you might need to check how many rows you are trying to retrieve. If your database server is not capable of processing big number of rows you might need to improve your hardware or CPU usage limits of your database daemon.