Page 81 - SQL

Chapter 23: Finding Duplicates on a Column

Subset with Detail

Remarks

• To select rows with out duplicates change the WHERE clause to "RowCnt = 1"

• To select one row from each set use Rank() instead of Sum() and change the outer WHERE
clause to select rows with Rank() = 1

Examples

Students with same name and date of birth

WITH CTE (StudentId, Fname, LName, DOB, RowCnt)
as (
SELECT StudentId, FirstName, LastName, DateOfBirth as DOB, SUM(1) OVER (Partition By
FirstName, LastName, DateOfBirth) as RowCnt
FROM tblStudent
)
SELECT * from CTE where RowCnt > 1
ORDER BY DOB, LName

This example uses a Common Table Expression and a Window Function to show all duplicate
rows (on a subset of columns) side by side.

Read Finding Duplicates on a Column Subset with Detail online:
https://riptutorial.com/sql/topic/1585/finding-duplicates-on-a-column-subset-with-detail

https://riptutorial.com/ 63