Question

I am trying to query data from two tables into one tables using OUTER JOIN. The thing is that to uniquely identify the rows, three fields are needed. This brings me to query containing this expression:

FROM Data1 DB
  RIGHT OUTER JOIN Data2 FT on (DB.field1 = FT.Value1 
                                and DB.field2 = FT.field2 
                                and DB.field3 = FT.field3)

However, the query runs for pretty much forever. To test the whole thing I used WHERE conditions and FULL OUTER JOIN and in the case of WHERE conditions it is done almost instantly whereas using the FULL OUTER JOIN I had the same trouble and usually ended up cancelling the whole thing after 5 minutes or so.

Can anyone see what I am doing wrong with my query? Thanks for any help!

Answer 1

Do you really need all the records back from the query? Some WHERE criteria could cut execution time down considerably.

Yes, and indexes. Check the plan and create recomended indexes.