----- Original Message -----
> From: "David Lerer" <[email protected]>
>
> Have you tried to set city = null (i.e. without the quotes)?
Spot on, I'd think.
NULL values are not a string with "NULL" in it - that's only what it looks like
in query results :-) An empty string ('') is to strings what 0 (zero) is for
integers: it says "the value of this field is nothing". NULL, on the other
hand, means "the value of this field is a total unknown", which is useful, for
example, in a field 'quantity': zero is still a valid, meaningful quantity;
whereas you would use NULL to indicate that you simply do not know the quantity.
It's a bit of a peculiar concept, but as David indicated, IS NULL will not
match fields set to the string "NULL" - as that is a string, not an unknown.
Another funny attribute of NULL is that NULL != NULL. There simply *is* nothing
to compare, so you cannot ever say it's equal.
--
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