LIMIT

The LIMIT clause sets the maximum number of rows returned by a query. It can improve query performance on large result sets by reducing the amount of data processed and returned.

Syntax

The basic syntax of the LIMIT clause is as follows:

SELECT column1, column2, ...
FROM table_name
LIMIT number_of_rows;

number_of_rows must be a non-negative integer. A negative value produces a planning error.

Examples

Consider the following table named "system_metrics":

+-------+-------+----------+-------------+-----------+---------------------+
| host  | idc   | cpu_util | memory_util | disk_util | ts                  |
+-------+-------+----------+-------------+-----------+---------------------+
| host1 | idc_a |     11.8 |        10.3 |      10.3 | 2022-11-03 03:39:57 |
| host1 | idc_b |       50 |        66.7 |      40.6 | 2022-11-03 03:39:57 |
| host1 | idc_c |     50.1 |        66.8 |      40.8 | 2022-11-03 03:39:57 |
| host1 | idc_e |     NULL |        66.7 |      40.6 | 2022-11-03 03:39:57 |
| host2 | idc_a |     80.1 |        70.3 |        90 | 2022-11-03 03:39:57 |
+-------+-------+----------+-------------+-----------+---------------------+

To retrieve the top three rows by memory_util, use the LIMIT clause:

SELECT host, idc, memory_util
FROM system_metrics
ORDER BY memory_util DESC
LIMIT 3;

The result of the above query would be:

+-------+-------+-------------+
| host  | idc   | memory_util |
+-------+-------+-------------+
| host2 | idc_a |        70.3 |
| host1 | idc_c |        66.8 |
| host1 | idc_b |        66.7 |
+-------+-------+-------------+

LIMIT n, m allows to select the m rows from the result after skipping the first n rows. The LIMIT m OFFSET n syntax is equivalent.

SELECT host, idc, memory_util
FROM system_metrics
ORDER BY memory_util DESC
LIMIT 2 OFFSET 1;

OR

SELECT host, idc, memory_util
FROM system_metrics
ORDER BY memory_util DESC
LIMIT 1, 2;

The result of the above query would be:

+-------+-------+-------------+
| host  | idc   | memory_util |
+-------+-------+-------------+
| host1 | idc_c |        66.8 |
| host1 | idc_b |        66.7 |
+-------+-------+-------------+