<< Dennis: I'm not sure how a multi-column index would work. My understanding is that you must reference both columns in a multi-column index in order for the index to be used (the fte article doesn't talk about multi-column very much). So let's say I have a PK column. Would I have to say "give me all rows where DateTime is null and PKColumn is not null?" >>
No, to get value from a multi-column index you must use indexable terms for columns starting with the left-most column in the index but you do not have to include all columns. For example, givenCREATE INDEX PPL_BDAY_LASTNAME ON People(BirthDate, LastName)then the following searches will use this index: WHERE BirthDate BETWEEN 1/1/12 and 12/31/12 -- left-most column of index WHERE BirthDate = 6/30/1960 AND LastName = 'Smith' -- left-most columns of index WHERE LastName = 'Smith' AND BirthDate = 6/30/1960 -- R:Base is smart enough to re-order the search. But this is would not use the index: WHERE LastName = 'Smith' -- Can't "peek into" the index beyond the first column -- Larry
