对工会使用与众不同的关键字 [英] Using distinct keyword with union

问题描述

尽管使用UNION和DISTINCT关键字，但查询中却出现重复行.

这是我的查询:

I am getting Duplicate rows in my query, despite using UNION and DISTINCT keywords.

Here is my query:

(SELECT DISTINCT A.AppointmentId,
                 u.Firstname,
                 u.Gender,
                 u.UserEmail,
                 u.PhoneNo,
                 a.PatientFirstName,
                 a.PatientLastName,
                 a.PatientGender,
                 a.Date,
                 a.TimeStart,
                 a.CompanyId,
                 C.CompanyName,
                 a.ProviderId,
                 a.TimeEnd,
                 a.Reason,
                 Ad.Line1,
                 Ad.Line2,
                 Ad.City,
                 Ad.State,
                 Ad.Zip
 FROM   Users u,
        Appointment a,
        Company C,
        Address Ad
 WHERE  u.UserId = a.UserId
        AND A.CompanyId = C.Id
        AND C.AddressId = Ad.Id
        AND A.ProviderId = '2EA0430F-3775-4623-92B1-5045CF836C11')
UNION
(SELECT DISTINCT A.AppointmentId,
                 E.Name AS FirstName,
                 E.Gender,
                 E.Email AS UserEmail,
                 E.PhoneNumber AS PhoneNo,
                 a.PatientFirstName,
                 a.PatientLastName,
                 a.PatientGender,
                 A.Date,
                 A.TimeStart,
                 A.CompanyId,
                 C.CompanyName,
                 A.ProviderId,
                 A.TimeEnd,
                 A.Reason,
                 Ad.Line1,
                 Ad.Line2,
                 Ad.City,
                 Ad.State,
                 Ad.Zip
 FROM   Appointment A,
        Employee E,
        Company C,
        Address Ad
 WHERE  A.ProviderId = '2EA0430F-3775-4623-92B1-5045CF836C11'
        AND C.AddressId = Ad.Id
        AND A.UserId = E.EmployeeId
        AND A.CompanyId = C.Id)
ORDER  BY A.Date DESC

Can anybody tell me why this is happening, and help me fix it?

推荐答案

UNION默认会删除不同的行.
检查您的联接，以确保没有重复项被返回.

UNION removes distinct rows by default.
Check your joins to ensure no duplicates are being returned.

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