Delete duplicate rows from a table and referenced table microsoft sql server - sql

Question

I have table Person :
PersonId | FirstName | LastName |
1 | 'John' | 'Doe' |
2 | 'Mike' | 'Test' |
3 | 'John' | 'Doe' |
4 | 'Mike' | 'Test' |
5 | 'John' | 'Doe' |
6 | 'John' | 'Doe' |
Table Customer :
CustomerId | PersonId |
1001 | 1 |
1002 | 2 |
1003 | 3 |
1004 | 4 |
1005 | 5 |
1006 | 6 |
I want to delete Customer 1003,1004,1005,1006 because their Persons are duplicate, but PersonId is not same.
This should check FirstName and LastName in Person table and delete the duplicates in Customer table , Then delete duplicates in Person table. ( 3,4,5,6 )
Sorry if similar questions has been asked before but I couldn't do this.

Answer 1

Check This.
We delete first from Customer table. First we find duplicate records by using Row_number() and deleting personid which have to rank more than 1.
Below Query show duplicate records :
select ROW_NUMBER () over ( partition by firstname,lastname order by
PersonId ) RID, PersonId,FirstName,LastName
from #Person
After finding Duplicates we delete it from customer table then Person.
delete from Customer where PersonId in
(
select distinct PersonId P from
( select ROW_NUMBER () over ( partition by firstname,lastname order by PersonId ) RID, PersonId,FirstName,LastName from #Person )a
where RID>1
)
delete from Person where PersonId in
(
select distinct PersonId P from
( select ROW_NUMBER () over ( partition by firstname,lastname order by PersonId ) RID, PersonId,FirstName,LastName from #Person )a
where RID>1
)

Answer 2

Use this query to view the duplicates:
with duplicatecte(personid,rownum)As
(
select personid ,
row_Number() over(partition by FirstName+LastName order by personid)
from #person
)
select b.personid,customerid from duplicatecte a
inner join #customer b on a.personid=b.personid where rownum>1
Modify this query to delete as below
with duplicatecte(personid,rownum)As
(
select personid ,
row_Number() over(partition by FirstName+LastName order by personid)
from #person
)
delete b
from duplicatecte a
inner join #customer b on a.personid=b.personid where rownum>1

Answer 3

Begin Tran
CREATE TABLE #Person(PersonId INT,FirstName NVARCHAR(50),LastName NVARCHAR(50))
CREATE TABLE #Customer (CustomerId INT,PersonId INT)
INSERT INTO #Person
SELECT 1,'John','Doe' UNION ALL
SELECT 2 ,'Mike','Test' UNION ALL
SELECT 3 ,'John','Doe' UNION ALL
SELECT 4 ,'Mike','Test' UNION ALL
SELECT 5 ,'John','Doe' UNION ALL
SELECT 6 ,'John','Doe'
INSERT INTO #Customer
SELECT 1001, 1 UNION ALL
SELECT 1002 ,2 UNION ALL
SELECT 1003 ,3 UNION ALL
SELECT 1004 ,4 UNION ALL
SELECT 1005,5 UNION ALL
SELECT 1006,6
GO
WITH CTE (PersonId, DuplicateCount)
AS
(
SELECT FirstName,
ROW_NUMBER() OVER(PARTITION BY FirstName,LastName ORDER BY FirstName,PersonId) AS DuplicateCount
FROM #Person
)
--Select * from CTE WHERE DuplicateCount>1
DELETE FROM CTE WHERE DuplicateCount >1
DELETE FROM #Customer WHERE PersonId NOT IN(SELECT PersonId FROM #Person)
Select * from #Person
SELECT * from #Customer
ROLLBACK TRAN

Answer 4

declare #tbl table
(pid int
)
;with cte
as
(
select t1.*,row_number() over (partition by firstname,lastname order by personid) as rownum
from
person t1
)
delete
from
cte
output deleted.personid into #tbl where rownum>1
delete from customer where personid in (select personid from #tbl)

Answer 5

This will work for you:
Declare #person As table
(
PersonId int,
FirstName varchar(25),
LastName varchar(25)
)
Declare #customer As table
(
CustomerId int,
PersonId int
)
Insert Into #person (PersonId,FirstName,LastName) values(1,'John','Doe')
Insert Into #person (PersonId,FirstName,LastName) values(2,'Mike','Test')
Insert Into #person (PersonId,FirstName,LastName) values(3,'John','Doe')
Insert Into #person (PersonId,FirstName,LastName) values(4,'Mike','Test')
Insert Into #person (PersonId,FirstName,LastName) values(5,'John','Doe')
Insert Into #person (PersonId,FirstName,LastName) values(6,'John','Doe')
Insert Into #customer(CustomerId,PersonId) values(1001,1)
Insert Into #customer(CustomerId,PersonId) values(1002,2)
Insert Into #customer(CustomerId,PersonId) values(1003,3)
Insert Into #customer(CustomerId,PersonId) values(1004,4)
Insert Into #customer(CustomerId,PersonId) values(1005,5)
Insert Into #customer(CustomerId,PersonId) values(1006,6)
select p.PersonId into #temp from #person p right join
(Select PersonId,FirstName,LastName, ROW_NUMBER() over (partition by FirstName,LastName Order by PersonId) rownumber
from #person ) a
on p.PersonId=a.PersonId where a.rownumber>1
delete from #customer where PersonId in (select PersonId from #temp)
delete from #person where PersonId in (select PersonId from #temp)
select *from #customer
select *from #person