問題描述

select truncate(a.lat, 2) as plat, truncate(a.lng, 2) as plng, temp.latt, temp.lngt from user_post as a inner join (select truncate(user_post.lat, 2) as latt, truncate(user_post.lng, 2) as lngt from user_post group by latt, lngt having count(latt) >= 4 and count(lngt)>= 4) as temp on (a.plat = temp.latt and a.plng = temp.lngt);

為什么會報unknown column ’a.plat’ in ON clause 這樣的錯誤？

問題解答

a別名指向的是表user_post，從你的語句中來看，user_post表中有lat字段，沒有plat字段。所以on條件中的a.plat是不對的。

加個括號試下：

select a.plat, a.plng, temp.latt, temp.lngt from (select truncate(lat, 2) as plat, truncate(lng, 2) as plng from user_post) as a inner join (select truncate(lat, 2) as latt, truncate(lng, 2) as lngt from user_post group by latt, lngt having count(latt) >= 4 and count(lngt)>= 4) as temp on a.plat = temp.latt and a.plng = temp.lngt;