Ognjen Blagojevic <ognjen@etf.bg.ac.yu> writes:
> When I browse through the list of employees:
> id id_dept name
> -------------------
> 1 1 Tom
> 2 1 Mike
> 3 2 Meggie
> 4 2 Marge
> 5 3 Bart
> 6 3 Lisa
> 7 4 Homer
> using LIMITed selects like:
> SELECT * FROM employee ORDER BY id_dept LIMIT 3
> SELECT * FROM employee ORDER BY id_dept LIMIT 3 OFFSET 3
> SELECT * FROM employee ORDER BY id_dept LIMIT 3 OFFSET 6
> it seems that Meggie is not in the result list on any of the SELECTs.
"ORDER BY id_dept" isn't a unique sort key. In this example the
implementation is free to return Meggie and Marge in either order,
and the ordering can indeed vary depending on the LIMIT/OFFSET values.
Moral: don't use LIMIT/OFFSET without a fully specified sort order.
regards, tom lane