Question

I have:

  SELECT  dv.VariableID ,
            ds.DataSourceID ,
            p.DataVariableDataSourceParamId ,
            p.ParamCode ,
            p.ParamDisplayName ,
            p.DVDSParamControlType ,
            p.DependentOnDVDSParamId ,
            pv.ParamValue
    FROM    dbo.DataVariable dv
            INNER JOIN dbo.DataVariableDataSource ds ON dv.DataSourceId = ds.DataSourceID
            INNER JOIN dbo.DataVariableDataSourceParam p ON ds.DataSourceID = p.DataSourceId
            INNER JOIN dbo.DataVariableDataSourceParamValue pv ON p.DataVariableDataSourceParamId = pv.DataVariableDataSourceParamId
    WHERE   dv.VariableID = @vid
    ORDER BY dv.VariableID

When I just have the first two joins, I get what I want: 6 results. When I add the third, I get 660. I just want the ParamValue for the 6 records from the first 2 joins and I can’t seem to figure out why this is breaking. I’m on my 12th hour of coding and I’m sure this is insanely obvious, but I could use a hand. Thanks in advance.

Answer 1

This is going to be because you have numerous rows in your pv table that match on DataVariableDataSourceParamId

You can verify by adding a SELECT DISTINCT. You may need to clean that table up or keep the distinct

However, the distinct will only help if pv.ParamValue is the same for all, otherwise you are rightfully getting more matches as what is happening is that you are finding all the matches for DataVariableDataSourceParamId and displaying them. If all those matches are the same value, then the distinct will indeed help, though