错误代码 1066 sqlstate 42000 不唯一表别名

Question

我收到此错误调用不唯一表别名，我无法找出问题所在。我有一个连接所有人的通用日期表。还有连接两个表的教师表 - 请假和出勤。请帮忙

SELECT
trns_teacherattendance.Attendance_Status,
trns_teacherattendance.Attendance_Month,
trns_teacherattendance.AcademicYear_Id,
trns_teacherattendance.School_Id,
trns_teacherattendance.Bio_Code,
trns_teacherattendance.IsActive,
mst_holiday_teacher.Holiday_Name,
dates.dates,
leave_new_view_teacher.Leave_Status,
mst_teacher.Teacher_Name,
leave_new_view_teacher.LeaveDate
FROM
trns_teacherattendancemapping
LEFT OUTER JOIN
trns_teacherattendance
ON
(
trns_teacherattendancemapping.Bio_Code =
trns_teacherattendance.Bio_Code)
RIGHT OUTER JOIN
dates
ON
(
trns_teacherattendance.Attendance_Date = dates.dates)
LEFT OUTER JOIN
mst_teacher
ON
(
trns_teacherattendancemapping.Teacher_Id =
mst_teacher.Teacher_Id)
RIGHT OUTER JOIN
leave_new_view_teacher
ON
(
mst_teacher.Teacher_Id = leave_new_view_teacher.TID)
LEFT OUTER JOIN
leave_new_view_teacher
ON
(
dates.dates = leave_new_view_teacher.LeaveDate)
LEFT OUTER JOIN
mst_holiday_teacher
ON
(
dates.dates = mst_holiday_teacher.Holiday_Date) ;

Answer 1

您leave_new_view_teacher将两次加入表，但您没有为其提供不同的别名。数据库无法知道要从哪个查询/表中引用列。每个联接可以拉取不同的数据/行。

为这些表分配别名作为本部分的最低要求：

RIGHT OUTER JOIN
leave_new_view_teacher AS lnvt1 -- here
ON
mst_teacher.Teacher_Id = leave_new_view_teacher.TID
LEFT OUTER JOIN
leave_new_view_teacher AS lnvt2 -- and here
ON
dates.dates = leave_new_view_teacher.LeaveDate

您还需要对SELECT部分中的列进行正确分类：

SELECT
...
lnvt1.Leave_Status, -- you're probably getting this from first join
mst_teacher.Teacher_Name,
lnvt2.LeaveDate -- this probably comes from second join

您也不需要每个ON子句的括号，因此我删除了它们。