Db2 Text Search multiple predicates

If a query contains multiple predicates, consider the following limitations depending on how the predicates are organized.

UNION versus OR operators

Query performance might improve by using UNION instead of OR to combine multiple predicates.

Using a JOIN

Text search functions can be a predicate in an outer join, with limitations for LEFT OUTER JOIN and FULL OUTER JOIN. For these cases a text search predicate can only be applied if the search on this text index can be joined back with the primary key of its base table. For example, the following type of query is supported:

select place.placenum, location.description from place 
LEFT OUTER JOIN location on (location.mgrid = place.ownerid)
where 
(location.description is null and contains(place.description, 'Paris')=1 )

The CONTAINS and SCORE functions are not supported as a predicate in a LEFT OUTER JOIN or FULL OUTER JOIN.