我想优化 sql 查询
SET SQL_BIG_SELECTS=1;
SELECT
`Surveys`.`fname`
, `Surveys`.`lname`
, `Surveys`.`smobile`
, `Surveys`.`semail`
, `Surveys`.`country`
, `Surveys`.`city`
, `Surveys`.`sdob`
, `Brand`.`brandname`
, `Product`.`productname`
, `Surveys`.`outletcode`
, `Surveys`.`outletname`
, `Surveys`.`coupon_no`
, `Users`.`username`
, DATE_ADD(`Surveys`.datetime, INTERVAL 8 HOUR) as datetime
, `Surveys`.`duration`
, userentry.couponcode as wcouponcode
, userentry.couponcodecountry
, userentry.prizename
, DATE_ADD(userentry.datetime, INTERVAL 8 HOUR) as wdatetime
FROM
`Surveys`
INNER JOIN `Brand`
ON (`Surveys`.`brandid` = `Brand`.`brandid`)
INNER JOIN `Product`
ON (`Surveys`.`productid` = `Product`.`productid`) AND (`Surveys`.`brandid` = `Product`.`brandid`)
INNER JOIN `Users`
ON (`Surveys`.`userid` = `Users`.`userid`)
INNER JOIN `userentry`
ON (`userentry`.`mobile` = `Surveys`.`smobile`)
如果我没有写 SET SQL_BIG_SELECTS=1; 它不起作用
即使使用 SQL_BIG_SELECTS 它的过期(sql 超时),
那么如何优化这个查询
请帮我