Ifthenelse not calling Sequence table

Hi,

I am having an issue with sequence table by calling sql in ifthenelse but no records inserting using below statement. Can you please let me know, if below statement is correct?

ifthenelse(sql( 'DS', 'SELECT count(*) FROM schemxxx1.PRF, schemxxx1.EPRF WHERE PRF.PRFNAME = EPRF.PRFNAME')=0, sql('DS','select schemxxx1.seqprocessfamilyid.nextval from dual'),PRF.PRF_ID)

As per above statement, the below condition works (Separated condition from above)

SELECT count(*) FROM schemxxx1.PRF, schemxxx1.EPRF WHERE PRF.PRFNAME = EPRF.PRFNAME')=0

As per above statement, the below condition doesn't works for inserting sequence id(Separated condition from above)

sql('DS','select schemxxx1.seqprocessfamilyid.nextval from dual')

Can please help me whether the above statement correct, if correct why sequence table not generating records?

Thanks in advance,

Sri