How to use ROW_NUMBER() with Subqueries In SQL
Utilize the ROW_NUMBER() function within subqueries to assign row numbers to dataset entries, enabling precise pagination.
Syntax:
SELECT * FROM (
SELECT columns, ROW_NUMBER() OVER (ORDER BY column_name) AS row_num
FROM table_name
WHERE conditions
)
WHERE row_num BETWEEN start_row AND end_row;
Let’s consider the table employees with columns employee_id, first_name, last_name, and salary. We’ll paginate through this table using this method
Example: Pagination using ROW_NUMBER() with Subqueries
SELECT * FROM (
SELECT employee_id, first_name, last_name, salary, ROW_NUMBER() OVER (ORDER BY employee_id) AS row_num
FROM employees
)
WHERE row_num BETWEEN 1 AND 3;
Output:
Pagination using ROW_NUMBER() with Subqueries
Explanation: This query retrieves the first 3 records from the employees table sorted by employee_id.
How to Pagination in PL/SQL?
Pagination is a technique used to divide large datasets into smaller, manageable chunks called pages. It’s important for improving user experience and optimizing database performance. In PL/SQL, pagination can be achieved using various methods, allowing users to navigate through query results efficiently.
In this article, we’ll explore how to efficiently manage large datasets in PL/SQL using pagination techniques. We’ll cover three methods: ROW_NUMBER() with Subqueries, Cursors with OFFSET and LIMIT, and Analytic Functions with ROWNUM. Each method is explained with examples to provide a clear understanding.