mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-29 19:12:03 +00:00
87 lines
2.3 KiB
Markdown
87 lines
2.3 KiB
Markdown
---
|
|
toc_title: OFFSET
|
|
---
|
|
|
|
# OFFSET FETCH Clause {#offset-fetch}
|
|
|
|
`OFFSET` and `FETCH` allow you to retrieve data by portions. They specify a row block which you want to get by a single query.
|
|
|
|
``` sql
|
|
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](../../../sql-reference/statements/select/limit.md) clause. For example, the following query
|
|
|
|
``` sql
|
|
SELECT * FROM test_fetch ORDER BY a OFFSET 1 ROW FETCH FIRST 3 ROWS ONLY;
|
|
```
|
|
|
|
is identical to the query
|
|
|
|
``` sql
|
|
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.
|
|
|
|
!!! note "Note"
|
|
According to the standard, the `OFFSET` clause must come before the `FETCH` clause if both are present.
|
|
|
|
!!! note "Note"
|
|
The real offset can also depend on the [offset](../../../operations/settings/settings.md#offset) setting.
|
|
|
|
## Examples {#examples}
|
|
|
|
Input table:
|
|
|
|
``` text
|
|
┌─a─┬─b─┐
|
|
│ 1 │ 1 │
|
|
│ 2 │ 1 │
|
|
│ 3 │ 4 │
|
|
│ 1 │ 3 │
|
|
│ 5 │ 4 │
|
|
│ 0 │ 6 │
|
|
│ 5 │ 7 │
|
|
└───┴───┘
|
|
```
|
|
|
|
Usage of the `ONLY` option:
|
|
|
|
``` sql
|
|
SELECT * FROM test_fetch ORDER BY a OFFSET 3 ROW FETCH FIRST 3 ROWS ONLY;
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─a─┬─b─┐
|
|
│ 2 │ 1 │
|
|
│ 3 │ 4 │
|
|
│ 5 │ 4 │
|
|
└───┴───┘
|
|
```
|
|
|
|
Usage of the `WITH TIES` option:
|
|
|
|
``` sql
|
|
SELECT * FROM test_fetch ORDER BY a OFFSET 3 ROW FETCH FIRST 3 ROWS WITH TIES;
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─a─┬─b─┐
|
|
│ 2 │ 1 │
|
|
│ 3 │ 4 │
|
|
│ 5 │ 4 │
|
|
│ 5 │ 7 │
|
|
└───┴───┘
|
|
```
|