Sparse Lookup query

Havoc · Post by **Havoc** » Wed Feb 07, 2007 11:02 am

In the DataStage Parallel Job Developer's Guide, they mention that when we have a user generated SQL query, we have to use sparse lookups. Is there a reason why they suggest this ?

On what basis does the lookup happen when the mode is Sparse Lookup. In my job, there are no key column matches in my Lookup to Oracle Sequence (sparse lookup mode) but I am getting the desired output (i.e the next sequence number). But I just wanted to know how Sparse Lookup runs 'behind the scenes' ? This question is more in reference to this post

This question is related more the to the replies i got for this query:-
viewtopic.php?t=107257

kumar_s · Post by **kumar_s** » Thu Feb 08, 2007 2:02 am

Query in Sparse lookup will be executed every time when each row enters the stage. And hence you get the new sequence number generated.
Increment of the sequence number is the job of Database not Datastage.

Havoc · Post by **Havoc** » Thu Feb 08, 2007 2:26 am

kumar_s wrote:Query in Sparse lookup will be executed every time when each row enters the stage. And hence you get the new sequence number generated.
Increment of the sequence number is the job of Database not Datastage.

Yeah, i got that ... but... on what are they doing the column matches? There is no key expression required for a sparse lookup atleast in this scenario. Then what exactly is it 'looking up' to ?

kumar_s · Post by **kumar_s** » Thu Feb 08, 2007 2:42 am

First available record in the lookup table's records set will be passed to the output along with incomming record set, if no lookup key is specified.
Else the matched row is processed among the existing record set. In your case, the available only row is the next sequence number.