Table containing the following values:
Column1 Column2 1 NULL NULL 4 2 NULL NULL 5 3 6
The following query:
SELECT SUM([Column1] + [Column2] ) FROM [myTable]
returns a value of
9 when it should be returning
21. Why? How does it arrive at the value?
I know the SUM can be corrected by adding
ISNULL like so:
SELECT SUM(ISNULL([Column1], 0) + ISNULL([Column2], 0)) FROM [myTable]
but I would like to know the logic behind the value
What is the sum of
null and a number, exactly? Note where the
9 comes from: the only row which has non-null
One viable solution has of course already been posted. But then, where's the fun in jumping right to the fix?
(copypasta'd at OP's request)