SQL Server ROW_NUMBER() Explained

1 year ago
Liam
2 minutes

The ROW_NUMBER() function in SQL Server is used to assign unique consecutive numbers to rows in a result set. It is commonly used for sorting and paging operations.

Grammar: the rules of a language that determine how words and sentences are structured.

ROW_NUMBER() OVER (ORDER BY column_name1 [, column_name2, ...])

Parameter Description:

  1. ORDER BY: Specifies which columns to sort by, you can specify multiple columns and separate them with commas.

For example, if there is a table called “employees” with columns: employee_id, first_name, and last_name. If we want to assign consecutive numbers to the rows in the result set in ascending order based on the first_name column, we can use the following query:

SELECT employee_id, first_name, last_name, 
    ROW_NUMBER() OVER (ORDER BY first_name) AS row_num
FROM employees

This will return a result set where each row contains employee_id, first_name, last_name, and row_num columns. The row_num column will contain consecutive numbers for the rows sorted in ascending order by the first_name column.

In actual practice, the ROW_NUMBER() function is often used in conjunction with other functions (such as RANK(), DENSE_RANK()) or conditional statements to achieve more complex sorting and pagination requirements.

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