Question

在mysql中像这样的sql

SELECT  record.id,
record.create_time AS finishTime,
   record.money,
   record.real_money AS realMoney,
   record.money-record.real_money AS discountMoney,
   record.out_flow_num AS outFlowNum,
   record.user_id AS userId,
   mp_order.order_number AS orderNum,
   mp_order.teacher_id AS teacherId,
   stc.small_type_name AS smallTypeName
  FROM mp_bill_record record 
JOIN
(
    SELECT bill_type, small_type, channel, small_type_name
  FROM mp_bill_small_type_channel
  WHERE type= 'CASH_CONSUME'
  AND is_delete= 0
  AND id= 60) stc
ON record.bill_type= stc.bill_type
AND record.small_type= stc.small_type
AND record.channel= stc.channel
LEFT JOIN mp_order ON record.common_id= mp_order.id
WHERE record.is_delete= 0
AND record.create_time>= '2018-12-24 00:00:00'
AND record.create_time< '2018-12-25 00:00:00'

使用ORDER BY record.id desc花费的时间超过30000ms。如果没有ORDER BY record.id desc，则需要300毫秒。而且，结果只有8行。

the explain with order by

the explain without order by

为什么通过sql命令花费这么多时间

0 个答案: