SQL Join query with OR Clause

问题

Need help in creating a SQL query. Little confused so asking question. Here is the situation:

I have one table say EmpInfo: EmpFirstName, EmpLastName, EmpID, EmpGender, EmpDOB, EmpAddress Table2 EmpMasterID: EmpID1, EmpId2, AbsoluteEmpID

EmpInfo contains sample data:

EmpFirstName | EmpLastName | EmpID | EmpGender | EmpDOB  | EmpAddress
First1       | Last1       | 10    |  M        | 1/1/92  | Addr1
First2       | Last2       | 20    |  F        | 1/12/92 | Addr2
First3       | Last3       | 30    |  F        | 1/12/94 | Addr3
First4       | Last4       | 40    |  M        | 1/2/94  | Addr4
First5       | Last5       | 60    |  M        | 1/1/91  | Addr5
First6       | Last6       | 70    |  F        | 1/12/92 | Addr6
First7       | Last7       | 80    |  F        | 1/12/95 | Addr7
First8       | Last8       | 90    |  M        | 1/2/97  | Addr8

EmpMasterID sample data:

EmpID1 | EmpId2 | AbsoluteEmpID
10     |  20    |  10
60     |  70    |  60

Now I have to join these 2 tables and get the following columns:

EmpID, EmpFirstName, EmpLastName, AbsoluteEmpID

The value of AbsoluteEmpID will be picked up from the EmpMasterID table if EmpInfo.EmpID = EmpMasterID.EmpID1 OR EmpInfo.EmpID = EmpMasterID.EmpID2 Otherwise the value of AbsoluteEmpID will be EmpID itself.

Please help.

Thanks.

回答1:

This will join either on EmpID1 or on EmpID2. If both fails, left join ensures you get a row with null and then you just replace null with empid:

select ei.EmpID, 
       ei.EmpFirstName, 
       ei.EmpLastName, 
       isnull(em.AbsoluteEmpID, ei.EmpID) as AbsoluteEmpID
from EmpInfo ei
left join EmpMasterID em on ei.empid = em.EmpID1 or ei.empid = em.EmpID2

回答2:

Should be based on an inner join

update EmpInfo 
INNER JOIN EmpMasterID On (EmpInfo.EmpID = EmpMasterID.EmpID1 
                           OR EmpInfo.EmpID = EmpMasterID.EmpID2)
SET EmpID = AbsoluteEmpID

回答3:

Why don't you just want this?

SELECT ei.EmpID, ei.EmpFirstName, ei.EmpLastName, em.AbsoluteEmpID
FROM EmpMasterID em JOIN
     EmpInfo ei
     ON ei.EmpID = ei.AbsoluteEmpID;

I don't see what OR has to do with this query.

来源：https://stackoverflow.com/questions/40706849/sql-join-query-with-or-clause

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sql

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jointable