mysql - 左连接——如何提高效率？

Question

我写了一个难以阅读的查询，而且恐怕效率会很差。在将每个表中的consumerid 与consumerdata.consumerid 匹配方面，可以更有效地编写此查询吗？

select 

consumerdata.consumerid, 
signupdate, 
city, 
state, 
year(DOB), 
topaffiliate, 
activestatus, 
lastuseddate,

(select sum(achload.transactionamount) from achload where achload.consumerid = consumerdata.consumerid) as Total_ACH,
(select sum(billpay.transactionamount) from billpay where billpay.consumerid = consumerdata.consumerid) as Bill_Pay,
(select sum(recharge.transactionamount) from recharge where recharge.consumerid = consumerdata.consumerid) as Revenue,
(select count(cash.consumerid) from Cash where cash.consumerid = consumerdata.consumerid) as Cash__TXNs,
(select sum(moneytransfer.transactionamount) from moneytransfer where moneytransfer.consumerid = consumerdata.consumerid) as Transfer,
(select sum(moneytransfer.commissionfeeamount) from moneytransfer where moneytransfer.consumerid = tbl_accounts_consumerdata.consumerid) as commission_fee,
(select count(interchangetransactions.transactiondescription) from interchangetransactions where interchangetransactions.transactiondescription = "Withdrawal" and interchangetransactions.consumerid = consumerdata.consumerid) as Withdrawals,
(select count(interchangetransactions.responsecode) from interchangetransactions where interchangetransactions.responsecode in (01) and interchangetransactions.consumerid = consumerdata.consumerid and interchangetransactions.transactiondescription = "Withdrawal") as Code_01,
(select count(interchangetransactions.responsecode) from interchangetransactions where interchangetransactions.responsecode in (02) and interchangetransactions.consumerid = consumerdata.consumerid and interchangetransactions.transactiondescription = "Withdrawal" ) as Code_02,
(select count(interchangetransactions.transactiondescription) from interchangetransactions where interchangetransactions.transactiondescription IN ("2 Cash Advance", "1 Cash Advance") and interchangetransactions.consumerid = consumerdata.consumerid) as Cash_Advance_Count,
(select count(interchangetransactions.transactiondescription) from interchangetransactions where interchangetransactions.transactiondescription IN ("Balance") and interchangetransactions.consumerid = consumerdata.consumerid) as Inquiry_Count,
(select sum(interchangetransactions.transactionamount) from interchangetransactions where interchangetransactions.transactiontypecode = 195 and interchangetransactions.consumerid = consumerdata.consumerid)  as Intnl_TXN_Sum,
(select count(interchangetransactions.transactionamount) from interchangetransactions where interchangetransactions.transactiontypecode = 195 and interchangetransactions.consumerid = consumerdata.consumerid)  as Intnl_TXN_Count


from
consumerdata

left join achload
on achload.consumerid=consumerdata.consumerid

left join  billpay
on billpay.consumerid = consumerdata.consumerid

left join recharge
on recharge.consumerid = consumerdata.consumerid

left join cash
on cash.consumerid = consumerdata.consumerid

left join moneytransfer
on moneytransfer.consumerid = consumerdata.consumerid

left join interchangetransactions
on interchangetransactions.consumerid = consumerdata.consumerid

where consumerdata.signupdate between date(20120101) and curdate()
group by consumerdata.consumerid order by signupdate asc;

Answer 1

由于您没有从任何事务表中选择任何内容，因此一个简单的改进就是删除所有 LEFT JOIN 子句。它们没有用于任何用途，因为您是从相关子查询中获取总计的。这会导致数据库在所有表之间创建巨大的叉积，然后在底部执行 GROUP BY 时将其丢弃。

另一种方法是连接计算每个事务表的分组总计的子查询，而不是关联子查询。

select 
    c.consumerid, signupdate, state, year(DOB), topaffiliate, activestatus, lastuseddate,
    IFNULL(Total_ACH, 0) AS Total_ACH, IFNULL(Bill_Pay, 0) AS Bill_Pay, IFNULL(Revenue, 0) AS Revenue, 
    IFNULL(Cash__TXNs, 0) AS Cash__TXNs, ...
FROM consumerdata AS c
LEFT JOIN (
    SELECT consumerid, SUM(transactionamount) AS Total_ACH
    FROM achload
    GROUP BY consumerid) AS a ON a.consumerid = c.consumerid
LEFT JOIN (
    SELECT consumerid, SUM(transactionamount) AS Bill_Pay
    FROM billpay
    GROUP BY consumerid) AS b ON b.consumerid = c.consumerid
LEFT JOIN (
    SELECT consumerid, SUM(transactionamount) AS Revenue
    FROM recharge
    GROUP BY consumerid) AS r ON r.consumerid = c.consumerid
LEFT JOIN (
    SELECT consumerid, COUNT(*) AS Cash__TXNs
    FROM Cash
    GROUP BY consumerid) AS cash ON cash.consumerid = c.consumerid
...
WHERE c.signupdate between DATE(20120101) and CURDATE()
ORDER BY signupdate ASC

我不确定哪种方式实际上会更快 - 这可能取决于注册日期超出您指定范围的消费者的交易表中有多少数据。尝试两者，看看哪个更好。