mysql 比较两个表以查找匹配的记录

Question

我正在尝试从 tbl_attn_temp 获取所有数据，其中 TraineeID 与 tbl_assigned TraineeID 或 tbl_instructor_info InstructorID。但我得到的所有数据都与 tbl_assigned TraineeID 匹配。 tbl_instructor_info 数据未显示或显示如下:

tbl_attn_temp

tbl_assigned

tbl_instructor_info

SELECT t1.*
FROM tbl_attn_temp t1, tbl_instructor_info t2, tbl_assigned t3
WHERE t1.TraineeID=t3.TraineeID or t2.InstructorID
GROUP by t1.traineeid, t1.attnDate

Answer 1

您的OR 条件是错误的。它应该像这样WHERE (t1.TraineeID = t3.TraineeID OR t1.TraineeID = t2.InstructorID)查询应该是这样的:

SELECT t1.*
FROM tbl_attn_temp t1, tbl_instructor_info t2, tbl_assigned t3
WHERE (t1.TraineeID = t3.TraineeID OR t1.TraineeID = t2.InstructorID)
GROUP by t1.traineeid, t1.attnDate