Find non Identical values using Group by in SQL Server - sql

Question

I need to find the Non-Identical values are exist in a particular Group. Kindly have a look in the following Table Contact
ContactId FirstName LastName Mobile
_________________________________________________
1 Emma Watsan 9991234567
2 Jhon Wick 8887654321
1 Emma Watsan 9990001111
Here I need to fetch the Emma Watsan and need to find the Mobile numbers are Identical (bool - bit) If both Mobile numbers are Identical than 1 otherwise 0.
I tried the following Query
SELECT COUNT(*) FROM Contact c
GROUP BY c.ContactId, c.FirstName, c.LastName
HAVING COUNT(*) >1
Kindly assist me how to find the result.

Answer 1

for get the infor related to Emma Watsan you could ue
select * from Contact
where ContactId in (
select c.ContactId FROM Contact c
group by c.ContactId
having COUNT(*) >1
)
for get the Contacts that have the same numebr
select c.ContactId, COUNT(distinct Mobile) FROM Contact c
group by c.ContactId
having COUNT(distinct Mobile)>1

Answer 2

Use Count(Distinct [Mobile]) to get the number of distinct mobile nmumbers per ContactId. And the use a CASE expression to give 0 or 1 based of the count. If count is greater than 1 then 0 else 1.
Query
select t.[Name], case when t.[Mobile] > 1 then 0 else 1 end as [Mobile_Identity] from(
select ContactId,
max([FirstName] + ' ' + [LastName]) as [Name],
count(distinct [Mobile]) as [Mobile]
from contacts
group by ContactId
)t;
And if you want to retrieve only the rows with multiple mobile numbers, then use a having clause.
select t.[Name], case when t.[Mobile] > 1 then 0 else 1 end as [Mobile_Identity] from(
select ContactId,
max([FirstName] + ' ' + [LastName]) as [Name],
count(distinct [Mobile]) as [Mobile]
from contacts
group by ContactId
having count(distinct [Mobile]) > 1
)t;

Answer 3

Try This:
create table Contacts(ContactId int,FirstName varchar(15),LastName varchar(15),Mobile bigint)
insert into Contacts
select 1 ,'Emma','Watsan',9991234567
union all
select 2,'Jhon','Wick',8887654321
union all
select 1,'Emma','Watsan',9990001111
select c.ContactId, c.FirstName, c.LastName,IIF(cnt>1,1,0)ISIdentitcal
from (
SELECT c.ContactId, c.FirstName, c.LastName,
COUNT(*)cnt FROM Contacts c
GROUP BY c.ContactId, c.FirstName, c.LastName)c

Answer 4

How about:
Select distinct a.ContactId, case when b.mobile is null then 0 else 1 end as [is_duplicate]
from Contact a
left join Contact b
on a.ContactId = b.ContactId
and a.mobile = b.mobile
and a.id <> b.id
Where [id] is the primary key column in the table (you should have one).
Hope this helps.
PS: the table isn't normalized properly - if the ContactIDs repeat, the first and last name should not be in the same table.

Answer 5

I would do it something like this...(sample table variable with data included)
DECLARE #TABLE TABLE (ContactID INT, Firstname VARCHAR(55), Lastname VARCHAR(55), Mobile VARCHAR(55));
INSERT INTO #TABLE VALUES (1, 'Emma', 'Watsan', '9991234567');
INSERT INTO #TABLE VALUES (2, 'Jhon', 'Wick', '8887654321');
INSERT INTO #TABLE VALUES (1, 'Emma', 'Watsan', '9990001111');
INSERT INTO #TABLE VALUES (1, 'Emma', 'Watsan', '9990001111');
SELECT
T1.FirstName + ' ' + T1.LastName AS Name
,T1.Mobile
,MAX(CASE WHEN T2.RowID IS NULL THEN 0 ELSE 1 END) AS Duplicate
FROM
(
SELECT
ROW_NUMBER() OVER (ORDER BY FirstName,LastName, Mobile) AS RowID
,*
FROM #TABLE
) T1
LEFT JOIN
(
SELECT
ROW_NUMBER() OVER (ORDER BY FirstName,LastName, Mobile) AS RowID
,*
FROM #TABLE
) T2
ON T1.ContactID = T2.ContactID
AND T1.Mobile = T2.Mobile
AND T1.RowID <> T2.RowID
GROUP BY T1.FirstName + ' ' + T1.LastName, T1.Mobile
;
If the actual table already has row numbers, than the row_number() function can be skipped and the actual row ID of the table used in its place.
In the example here, Emma Watsan has the same number twice (on purpose), and another number that shows only once in the table. The duplicate mobile number is marked (Duplicate = 1), but the other numbers are not, as desired.