【MySQL幫助】幫朋友優化SQL的過程--)從4S到0.011秒

這個sql運行很慢，4秒鐘

SELECT 
(op.cash_payment+op.pos_payment+op.online_payment+op.charge_card_payment) AS real_payment,op.* 
FROM db_order.`order_payment` AS op WHERE op.order_payment_id in 
(SELECT oi.order_payment_id FROM db_order.`order_info` AS oi WHERE oi.batch_order_id = '123456') 
ORDER BY op.insert_time DESC

SELECT 
  (op.cash_payment+op.pos_payment+op.online_payment+op.charge_card_payment) AS real_payment,op.* 
  FROM db_order.`order_payment` AS op,db_order.`order_info` oi WHERE op.order_payment_id=oi.order_payment_id and oi.batch_order_id = '123456'
  ORDER BY op.insert_time DESC

發給朋友，朋友說相當快，在0.011S。

看來 這個IN確實需要謹慎使用，特別是在兩表關聯的時候，應該把in替換成內鏈接