LIMIT
and OFFSET
LIMIT
and OFFSET
allow you to retrieve just
a portion of the rows that are generated by the rest of the query:
SELECTselect_list
FROMtable_expression
[ ORDER BY ... ] [ LIMIT {number
| ALL } ] [ OFFSETnumber
] SELECTselect_list
FROMtable_expression
[ ORDER BY ... ] [ LIMIT [number,
] {number
| ALL } ]
If a limit count is given, no more than that many rows will be
returned (but possibly fewer, if the query itself yields fewer rows).
LIMIT ALL
is the same as omitting the LIMIT
clause, as is LIMIT
with a NULL argument.
OFFSET
says to skip that many rows before beginning to
return rows. OFFSET 0
is the same as omitting the
OFFSET
clause, as is OFFSET
with a NULL argument.
If both OFFSET
and LIMIT
appear, then OFFSET
rows are
skipped before starting to count the LIMIT
rows that
are returned.
When using LIMIT
, it is important to use an
ORDER BY
clause that constrains the result rows into a
unique order. Otherwise you will get an unpredictable subset of
the query's rows. You might be asking for the tenth through
twentieth rows, but tenth through twentieth in what ordering? The
ordering is unknown, unless you specified ORDER BY
.
The query optimizer takes LIMIT
into account when
generating query plans, so you are very likely to get different
plans (yielding different row orders) depending on what you give
for LIMIT
and OFFSET
. Thus, using
different LIMIT
/OFFSET
values to select
different subsets of a query result will give
inconsistent results unless you enforce a predictable
result ordering with ORDER BY
. This is not a bug; it
is an inherent consequence of the fact that SQL does not promise to
deliver the results of a query in any particular order unless
ORDER BY
is used to constrain the order.
The rows skipped by an OFFSET
clause still have to be
computed inside the server; therefore a large OFFSET
might be inefficient.
For compatibility with MySQL, LightDB also supports the LIMIT offset, row_count
syntax.