Question

If I use something like this inside an UPDATE instruction and I want to check if the functions returns ‘N’, so set ‘ ‘:

ta.COD_ACT_MCH= ALIMENTATION_COD_ACT_MCH(ta.CA_DDE_TYP_DDE,tb.COD_SECVTE,tb.NUM_FOU1,ta.CA_COD_ENSCIAL)

is this the way to do it? or it calls the function twice? How can I optimize this?

   ta.COD_ACT_MCH=DECODE( ALIMENTATION_COD_ACT_MCH(ta.CA_DDE_TYP_DDE,tb.COD_SECVTE,tb.NUM_FOU1,ta.CA_COD_ENSCIAL),
'N',
' ',
ALIMENTATION_COD_ACT_MCH(ta.CA_DDE_TYP_DDE,tb.COD_SECVTE,tb.NUM_FOU1,ta.CA_COD_ENSCIAL))

Answer 1

This hack will work unless ALIMENTATION_COD_ACT_MCH can return NULL:

NVL(NULLIF(
  ALIMENTATION_COD_ACT_MCH(ta.CA_DDE_TYP_DDE,tb.COD_SECVTE,tb.NUM_FOU1,ta.CA_COD_ENSCIAL),
  'N'), '')