SELECT *
FROM `placement_ans` A, `placement_quiz` B
left join `placement_time` C on (A.state=C.state)
where
A.no_place=C.no_place and A.no_stu=C.no_stu and A.no_place=B.no_place and A.place_q=B.no_q and YEAR(A.place_date) = YEAR(curdate()) and MONTH(A.place_date) = MONTH(curdate()) and A.no_place=208 and A.no_stu=793 order by A.place_q ASC
错误是 “on 子句”中的未知列“A.state”
我也尝试过使用
SELECT *
FROM `placement_ans` A, `placement_quiz` B
left join `placement_time` C on (placement_ans.state=C.state)
where
A.no_place=C.no_place and A.no_stu=C.no_stu and A.no_place=B.no_place and A.place_q=B.no_q and YEAR(A.place_date) = YEAR(curdate()) and MONTH(A.place_date) = MONTH(curdate()) and A.no_place=208 and A.no_stu=793 order by A.place_q ASC
但它似乎不想工作
我有一张像这样的 table
placement_time
state num
100 10
和
placement_ans
state something
100 11
100 22
55 33
22 55
33 77
我想打印出一个表格
placement_ans
state something num
100 11 10
100 22 10
55 33 null
22 55 null
33 77 null
最佳答案
根据给定的示例数据集和预期结果,您不需要引用表placement_quiz
,可以这样做
select a.*,b.num from placement_ans a
left join placement_time b on b.state = a.state
关于mysql - 左连接出现 "unknown column"错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29722833/