Question

I have the following data :

SectorKey Sector foo   1         A      null  2         B      null ...       ...    ... 1         null   a   2         null   b  2         null   c  1         null   d  2         null   e  ...       ...    ... 

I want to update column Sector when it’s null based on the value of sectorKey, ie I want Sector to be ‘A’ when SectorKey is 1 and ‘B’ when SectorKey is 2

I’ve tried this query :

update tbFoo set Sector=A.sector  from tbFoo A INNER JOIN tbFoo B ON A.SectorKey=B.SectorKey  and A.Sector is not null  and B.Sector is null 

and got this error message :

The table ‘tbFoo’ is ambiguous.

I’ve tried to alias the first tbFoo, but it doesn’t seem to be a valid syntax. I don’t understand why SQLServer complains about an ambiguous naming since I’ve got all my tables aliased.

I’ve found this thread, and I feel like I’m doing exactly the same thing as in the upvoted answer. I’ve also tried the query suggested in the accepted answer :

    update tbFoo A     set Sector =         (select Sector from tbFoo          where A.SectorKey=SectorKey and Sector is not null) 

and then SQLServer complains about an incorrect syntax near ‘A’

Any ideas on what may be happening, and to fix this? I’m using SQLServer 2008.

EDIT I’ve not shown the total data of my table. I don’t have only two cases (A and B), but rather a few thousands of cases. So an explicit case is not an option

Answer 1

Use the alias in the first part of your update query:

update B set Sector=A.sector  from tbFoo A INNER JOIN tbFoo B ON A.SectorKey=B.SectorKey  and A.Sector is not null  and B.Sector is null 

Otherwise it doesn’t know which instance of the table to update.