NULLIF

NULLIF returns NULL if the two arguments are equal; otherwise NULLIF returns the first argument.

   NULLIF(x,y) = NULL if x=y
   NULLIF(x,y) = x if x != y

NULLIF can be used to replace a specific value with NULL. In this example the party Lab is replaced with NULL.

SELECT name, party
      ,NULLIF(party,'Lab') AS aff
  FROM gisq.msp WHERE name LIKE 'C%'

SELECT name, party
      ,NULLIF(party,'Lab') AS aff
  FROM msp WHERE name LIKE 'C%'

Anonymous