Please explain with an example the difference between null
and empty string. ALso the difference between '1' and "1".

Null is an absence of a value. An empty string is a value, but is just empty. Null is special to a database. The difference between '1' and "1" for in a database query is that the SQL syntax supports '1' for SQL queries, but doesn't use "1".

Brian

Can any body give me an example when to use null and empty string.
I dont understand at what situation we can use them. Actually
it doesnot make me sense. I hope someone give will give me example
and explain the answer. Thanks.
shoakat

well, IMO, NULL isn't allocated any memory, the string with NUll value is just a pointer which is pointing to nowhere in memory. however, Empty IS allocated to a memory location, although the value stored in the memory is "".
it is up to you when to use empty or null if the field type is char.
save memory, shouldn't?

Null has no bounds, it can be used for string, integer, date, etc. fields in a database. Empty string is just regarding a string; it's a string like 'asdfasdf' is, but is just has no length. If you have no value for a field, use null, not an empty string.

Null is the database's determination of an absense of a value logically, so to speak. You can query like: where FIELD_NAME is NULL

Brian