OFFSET FETCH Clause
OFFSET
and FETCH
allow you to retrieve data by portions. They specify a row block which you want to get by a single query.
OFFSET offset_row_count {ROW | ROWS}] [FETCH {FIRST | NEXT} fetch_row_count {ROW | ROWS} {ONLY | WITH TIES}]
The offset_row_count
or fetch_row_count
value can be a number or a literal constant. You can omit fetch_row_count
; by default, it equals to 1.
OFFSET
specifies the number of rows to skip before starting to return rows from the query result set.
The FETCH
specifies the maximum number of rows that can be in the result of a query.
The ONLY
option is used to return rows that immediately follow the rows omitted by the OFFSET
. In this case the FETCH
is an alternative to the LIMIT clause. For example, the following query
SELECT * FROM test_fetch ORDER BY a OFFSET 1 ROW FETCH FIRST 3 ROWS ONLY;
is identical to the query
SELECT * FROM test_fetch ORDER BY a LIMIT 3 OFFSET 1;
The WITH TIES
option is used to return any additional rows that tie for the last place in the result set according to the ORDER BY
clause. For example, if fetch_row_count
is set to 5 but two additional rows match the values of the ORDER BY
columns in the fifth row, the result set will contain seven rows.
According to the standard, the OFFSET
clause must come before the FETCH
clause if both are present.
The real offset can also depend on the offset setting.
Examples
Input table:
┌─a─┬─b─┐
│ 1 │ 1 │
│ 2 │ 1 │
│ 3 │ 4 │
│ 1 │ 3 │
│ 5 │ 4 │
│ 0 │ 6 │
│ 5 │ 7 │
└───┴───┘
Usage of the ONLY
option:
SELECT * FROM test_fetch ORDER BY a OFFSET 3 ROW FETCH FIRST 3 ROWS ONLY;
Result:
┌─a─┬─b─┐
│ 2 │ 1 │
│ 3 │ 4 │
│ 5 │ 4 │
└───┴───┘
Usage of the WITH TIES
option:
SELECT * FROM test_fetch ORDER BY a OFFSET 3 ROW FETCH FIRST 3 ROWS WITH TIES;
Result:
┌─a─┬─b─┐
│ 2 │ 1 │
│ 3 │ 4 │
│ 5 │ 4 │
│ 5 │ 7 │
└───┴───┘