Difference between Lookup and joiner transformation in Informatica
Look up transformation :
a) Look up transformation can be used on a single table or a query to search for records that match incoming records. Matching condition can be specified in the lookup transformation. The result returned can be multiple columns or single column.
b) Lookup transformation can be unconnected or connected transformation. Unconnected transformation can return only single value.
c) Lookup transformation can be static or active. Dynamic lookups are active transformation.
d) Lookup transformation be used with more than one relational operator such as > , =, etc.
Joiner transformation :a) Joiner transformation is used to usually to join data coming from two separate tables or source qualifiers.
b) The join can be left outer join, inner join, right outer join, etc.
c) The joiner returns all the results that match the join condition.
d) The master records in the joiner transformation is cached. The detail records are not cached. Hence, joiner transformation is active transformation.
When do you use joiner or lookup transformation?
a) If the table size is not too large then preferable to use lookup.
b) If result from a single matching records needs to be returned then use a lookup. If there is a query that needs to be used in a lookup to find the result for lookup then good to use a lookup.
c) If you are doing lookup on a table that is updated in the session then use a lookup. Joiners are active so not preferable.
d) If look up table data does not change then the table can be made persistent and used in the lookup which gives even better performance.
e) If data from two different source qualifiers need to be joined then use a joiner.
f) If data from two different databases are read and need to be joined with a outer or inner join then use joiner transformation.