How do I use ROW_NUMBER()?

sql

prompt-engineering

join

paging

byAnton Shumikhin·Jan 22, 2025

ROW_NUMBER() function assigns a unique, sequential identifier for each row in a dataset. It's coupled with OVER() clause which determines the partitioning and ordering of records.

Here's a simple demonstration:

SELECT 
  ROW_NUMBER() OVER (ORDER BY column_name) AS row_number,  --row numbers go brr
  your_data
FROM 
  your_table;

ROW_NUMBER() labels rows starting from 1, OVER() tailors ordering by the column_name, and the result is stored in the row_number column.

⚠️ Pro tip: For large tables, contemplate using sysindexes for expedited row count:

SELECT rows FROM sysindexes WHERE id = OBJECT_ID('your_table') AND indid < 2;  --Not all super heroes wear capes

One row to rule them all

To target a specific row in an ordered set:

-- Retrieve the 5th row
SELECT * FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY Id) AS RowNum, *
  FROM User
) AS RowResults
WHERE RowNum = 5;  --Fifth time's the charm

For operations relative to a current position, such as finding a row 5 positions back:

-- Pro tip: Do not attempt without a coffee
SELECT * FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY Id) AS Row, Id, Field1, Field2, Field3 
  FROM User 
) AS us 
WHERE Row = CurrentRow - 5;

Mastering Order and Chaos

Take advantage of ROW_NUMBER() in conjunction with WHERE clause to filter and sort:

-- Get row for a specific username 
SELECT row_number, UserName
FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY JoinDate) AS row_number,  --JoinDate, the unsung hero
  UserName 
  FROM User
) AS OrderedUsers
WHERE UserName = 'JaneDoe';  --JaneDoe, the infamous

Deploy MIN or MAX with ROW_NUMBER() to pin down first or last row number:

-- Sneaky tip: 1st row vouches for the initial coffee
SELECT MIN(row_number) AS FirstRowNumber
FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY JoinDate) AS row_number
  FROM User
) AS NumberedTable;

Note: Always validate your syntax and ensure correct column names in the ORDER BY clause when using ROW_NUMBER().

Secret Diaries of ROW_NUMBER()

Paging like a boss

For efficient pagination, here's how ROW_NUMBER() can fetch you a particular page of results:

-- Grab the 3rd page, 10 rows per page
WITH Pagination AS (
  SELECT ROW_NUMBER() OVER (ORDER BY Id) AS RowNum, * 
  FROM User
)
SELECT * FROM Pagination
WHERE RowNum BETWEEN 21 AND 30;  --Catch me if you can

Fancy grouping, sans sweat

Group related rows and assign unique numbers to each subset. No sweat:

SELECT groupId, 
ROW_NUMBER() OVER(PARTITION BY groupId ORDER BY Id) AS RowNumber  --GROUP BY who?
FROM User;

Pinning top performers

And finally, select the top N records for each group with ROW_NUMBER():

;WITH Ranking AS (
  SELECT Id, Username, ROW_NUMBER() OVER(PARTITION BY UserType ORDER BY Reputation DESC) AS Rank  --User reputation battle royale
FROM User
)
SELECT * FROM Ranking
WHERE Rank <= 3;  --Top 3 on the podium