My Select SUM query returns null. It should return 0

Question

I\'m trying to sum up Customer balances using the following query:

select sum(balance) from mytable where customer = \'john\' 

However, if

Answer 1

Try this:

select sum(IsNull(balance,0)) from mytable where customer = 'john' 

Answer 2

select coalesce(sum(coalesce(balance,0)),0) from mytable where customer = 'john' 

Answer 3

Try this:

select COALESCE(sum(balance),0) from mytable where customer = 'john' 

This should do the work. The coalesce method should return the 0.

Answer 4

That's not a problem. If there are no rows, sum() will return null. It will also return null if all rows have a null balance.

To return zero instead, try:

select isnull(sum(balance),0) from mytable where customer = 'john' 

Answer 5

Maybe you are thinking of COUNT's behaviours?

COUNT(Field) will return 0 but SUM(Field) returns NULL if there are no matching rows.

You need an ISNULL or COALESCE

COALESCE or ISNULL