SQL SERVER: Generate Row Number/Serial Number without ordering by any columns

Introduction: In this article i am going to explain how to generate row number/serial number with the result set returned by the select query  without using any column in the order by clause. 

In Previous articles i explained Query to search any text in all stored procedures,views and functions and Auto generate auto incremented alphanumeric sequential code in sql server and CTE recursive query to get employee manager hierarchy with level and Without primary key column update first or last n records in table

Description: ROW_NUMBER() function is used to generate a serial/row number for a given record set returned by the select query. We have to use ORDER BY clause along with ROW_NUMBER() function to generate row numbers so that the numbers are assigned to the specific order.

We have learned that way in previous article How to Generate Row Number/Serial Number with each row. In that article row number was generated based on the column we put in order by clause. But what if we don’t want to sort the records and still want to generate row number ? There is a way , we can use dummy sub query column inside the ORDER BY clause. 

So In this article, we will learn how to generate row number without using any column in ORDER BY clause.

Implementation: Let's understand by an example:

IF OBJECT_ID('tempdb..#tbEmployee') IS NOT NULL

DROP TABLE #tbEmployee 

CREATE TABLE #tbEmployee

(

EmployeeName VARCHAR(100),

Age INT

) 

--Insert some dummy data

INSERT INTO #tbEmployee (EmployeeName,Age)

VALUES

('Neeraj',24),

('Abhay',23),

('Arjun',24),

('Bharat',25),

('Simran',23),

('Kashish',22),

('Rohan',25)

--View table data

SELECT * FROM #tbEmployee

EmployeeName	Age
Neeraj	24
Abhay	23
Arjun	24
Bharat	25
Simran	23
Kashish	22
Rohan	25

--Generate row/serial number without ordering the result by any column

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) AS SrNo, * FROM #tbEmployee

--Note: we can use any constant value e.g. 0, 1, 25, 100,null or

--any character or string value to generate row/serial number without ordering the result by any column

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS SrNo, * FROM #tbEmployee

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 100)) AS SrNo, * FROM #tbEmployee

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS SrNo, * FROM #tbEmployee

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 'a')) AS SrNo, * FROM #tbEmployee

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 'hello')) AS SrNo, * FROM #tbEmployee

SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NEWID())) AS SrNo, * FROM #tbEmployee

Result will be same for all of the above queries as:

SrNo	EmployeeName	Age
1	Neeraj	24
2	Abhay	23
3	Arjun	24
4	Bharat	25
5	Simran	23
6	Kashish	22
7	Rohan	25

Row number is generated for each row but records are in the same order that were added in the table.

Now over to you:

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