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Question

I am a bit stuck , Can any one help me here. I have two tables with the below structure.

Table 1
Id String
Code1 String
Code2 String

Table 2
Id String
UserCode String
UniversalCode String

What i need to do is to replace all value in code1 and code2 with UniversalCode from the table 2. To be more clear , if code1 matches UserCode then repalce Code1 with universalCode and again for the same record if code2 matches with usercode then replace it with UniversalCode. If there is no match retain the value for code1 and code2. I need to have all records from table 1. Table 1 and Table 2 are connected via Id.

I tried the below for one column but got stuck adding code2

SELECT 
Id,
CASE WHEN a.Code1 = b.UserCode then b.UniversalCode else a.Code1 end
from table1 a
LEFT OUTER JOIN table2 b ON (a.Id = b.Id and a.code1 = b.UserCode);

Any suggestions to get this done ? , The real scenario has 5-6 columns where i need to apply the same logic.

Test Data 

Table 1
1,123,ABCD
1,ABCD,123
1,456,BCD
1,BCD,789
1,789,100

Table 2 
1,123,XXX
1,456,YYY
1,789,ZZZ
2,123,XXX
2,456,YYY
2,789,ZZZ

Output 
1,XXX,ABCD
1,ABCD,XXX
1,YYY,BCD
1,BCD,ZZZ
1,ZZZ,100


output with a.id=b.id in Join(Please refer below comments for this output)
1       123     XXX     100     100
1       123     123     100     100
1       123     123     100     100
1       ABCD    ABCD    101     101
1       ABCD    ABCD    101     101
1       ABCD    ABCD    101     101
1       456     456     DEF     DEF
1       456     YYY     DEF     DEF
1       456     456     DEF     DEF
1       BCD     BCD     789     789
1       BCD     BCD     789     789
1       BCD     BCD     789     ZZZ
1       789     789     CDE     CDE
1       789     789     CDE     CDE
1       789     ZZZ     CDE     CDE
1       100     100     HBT     HBT
1       100     100     HBT     HBT
1       100     100     HBT     HBT
1       100     100     123     XXX
1       100     100     123     123
1       100     100     123     123

Answer 1

I'm not sure if I understand you but something like this should help you.

SELECT 
     a.Id
   , CASE WHEN a.Code1 = b.UserCode THEN b.UniversalCode ELSE a.Code1 END AS Code1
   , CASE WHEN a.Code2 = b.UserCode THEN b.UniversalCode ELSE a.Code2 END AS Code2
FROM    table1 a
    LEFT OUTER JOIN 
        table2 b 
        ON a.Id = b.Id;

Answer 2

We can try the below query:-

 SELECT 
    Id,
    CASE WHEN Code1 = UserCode then UniversalCode else Code1 end,
    CASE WHEN Code2= UserCode then UniversalCode else Code2 end
    from
    (select a.id,a.Code1,a.Code2,b.UserCode,b.UniversalCode
    from table1 a
    LEFT OUTER JOIN table2 b ON (a.Id = b.Id and a.code1 = b.UserCode) union 
    select a.id,a.Code1,a.Code2,b.UserCode,b.UniversalCode
    from table1 a
    LEFT OUTER JOIN table2 b ON (a.Id = b.Id and a.code1 = b.UniversalCode)) dat ;