Hi, I would like to use some indexes with functions like substr : CREATE INDEX IND1 ON T1 ( substr( col1, 1, 5 ) )... What are the performance of such an index compared to an index on col1... In which cases will this index be used in a query : Does the where clause has to match exactly the function used when creating the index : SELECT ... WHERE substr( col1, 1, 5 ) = '.....'. Do you recommend or not to use this kind of indexes ? Excuse me it it's not really clear but if necessary, I will try to explain it better... Thanks a lot Patrick FICHE
