SQL Oracle Limit

Introduction

In SQL, the LIMIT clause is used to restrict the number of results returned by a SQL query. In Oracle, the equivalent to LIMIT is the ROWNUM keyword, which is used to limit the number of rows returned by a query.

Syntax

The syntax for using ROWNUM in Oracle is as follows:

SELECT column1, column2, ...
FROM table_name
WHERE condition
AND ROWNUM <= number_of_rows;

The SELECT statement is used to select the columns from the specified table_name. The WHERE clause is used to specify any conditions that the rows must meet in order to be included in the result set. The ROWNUM keyword is used to limit the number of rows returned.

Example

Suppose we have a table called employees with the following data:

| id | name | age | |----|------|-----| | 1 | John | 25 | | 2 | Jane | 30 | | 3 | Bob | 27 | | 4 | Mary | 35 | | 5 | Tom | 22 |

To select the first two rows of this table using ROWNUM, we would use the following query:

SELECT id, name
FROM employees
WHERE ROWNUM <= 2;

This would return the following result:

| id | name | |----|------| | 1 | John | | 2 | Jane |

Note that ROWNUM is evaluated before the ORDER BY clause, so if you want to retrieve the first n rows in a specific order, you need to use a subquery.

Conclusion

In Oracle, the ROWNUM keyword is used to limit the number of rows returned by a SQL query. It is equivalent to the LIMIT clause used in other SQL dialects. By using ROWNUM, you can easily restrict the number of results returned by a query and improve the performance of your application.