Tuesday, June 25, 2013

How to select first ‘n’ records from a table?

Posted by Rahul Kharde at 9:49 PM
The SELECT TOP clause is used to specify the number of records to return. The SELECT TOP clause can be very useful on large tables with thousands of records. Returning a large number of records can impact on performance.

Example

CREATE TABLE [dbo].[Emp]
(
      [EmpID] [int] IDENTITY(1,1) NOT NULL,
      [EmpName] [varchar](50) NULL,
)

INSERT INTO EMP(EmpName)VALUES('ABC')
INSERT INTO EMP(EmpName)VALUES('CDE')
INSERT INTO EMP(EmpName)VALUES('PQR')
INSERT INTO EMP(EmpName)VALUES('XYZ')
INSERT INTO EMP(EmpName)VALUES('NML')

 With Top Clause SELECT Top 3 Records

SELECT Top 3 * FROM Emp

Without TOP Clause 

SELECT * FROM Emp e1
WHERE (SELECT COUNT(*) FROM Emp e2 WHERE e2.EmpID<e1.EmpID)<3

Output

Emp_ID
Emp_Name
1
ABC
2
CDE
3
PQR



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