NVL (Null Values)

[sukishan]

NVL takes two arguments and returns the first value that is not null.

  NVL(x,y) = x if x is not NULL
  NVL(x,y) = y if x is NULL

NVL can be useful when you want to replace a NULL value with some other value. In this example you show the name of the party for each MSP that has a party. For the MSP with no party (such as Canavan, Dennis) you show the string None.
SELECT name, party
      ,NVL(party,'None') AS aff
  FROM msp WHERE name LIKE 'C%'

--Try--
SELECT name, party
      ,NVL(party,'None') AS aff
  FROM msp WHERE name LIKE 'C%'