Replace NULL value

Is it possible to update NULL value?
My datatype for the field is float

i tried:

update table1
set [value1] = '0'
where [value1] = ''

however it does not replace the null value.
So what is the sql statement?
Thanks

Try using this.This Shld.Work

update table1
set [value1] = 0
where [value1] is null

You have to remember null is a special value. nothing equals null not even null:
select null = null ; ->false
select null = "" ; ->false

The way to find nulls one must use the word is
select null is null; -> true

Thanks a lot
U guys are wonderful

Instead of dealing with nulls after they are insterted into the table, you can use ISNULL

e.g.

INSERT INTO Bananas (monkeyid)
SELECT ISNULL(monkeyid,0)
FROM Monkeys

This will insert a 0 if monkeyid is null.

quite comical ...and also 100% correct, remember that a 0 length string is not the same as null data...which is what you were using here (a 0 length string)