I need something like this to work....

I have a column on which there are blanks spaces in a column instead of null.... I need to create a view on it where I replace all the blank spaces with NULL... I wrote a query like this but it is not working...Any suggestions??


SELECT
X.Column1,
X.Column2,
X.Column3,
CASE
WHEN X.column4= ' '
THEN NULL
ELSE X.Column4
END AS COLUMN4a,
FROM

( SELECT * FROM XYZ; ) AS X

Try...
NULLIF(x.column4 , '') AS column4a

it worked ..Thanks