Query for finding duplicates

Question

I am having a table with following schema:

CUSTOMERS (id INT, name VARCHAR(10), height VARCHAR(10), weight INT)

id is the primary key. I want to find out rows in which people who are having exactly same name, same height and same weight. In other words, I want to find out duplicates with-respect-to name, height and weight.

Example table:

1, sam, 160, 100
2, ron, 167, 88
3, john, 150, 90
4, sam, 160, 100
5, rick, 158, 110
6, john, 150, 90
7, sam, 166, 110

Example Output:

Now since there are people with same name, same height and same weight:

sam (id=1), sam (id=4)

and

john (id=3), john (id=6)

I want to get these ids. It is also okay if I get only one id per match (i.e. id=1 from first match and id=3 from second match).

---

I am trying this query but not sure if it is correct or not.

SELECT id
FROM customers
GROUP BY name, height, weight

Answer 1

Try this (valid for sql server):

SELECT 
    t.NAME,
    'Ids = '+
    (
        SELECT cast(Id as varchar)+',' 
        FROM Customers c 
        WHERE c.NAME = t.NAME AND c.Weight = t.Weight AND c.Height = t.Height
        FOR XML PATH('')
    )
FROM
(
    SELECT Name, height, weight
    FROM Customers
    GROUP BY Name, height, weight
    HAVING COUNT(*) > 1
) t

OR

as you asked - only one Id per match

SELECT 
    t.NAME,
    c.Id
FROM
(
    SELECT Name, height, weight
    FROM Customers
    GROUP BY Name, height, weight
    HAVING COUNT(*) > 1
) t
JOIN Customers c ON t.NAME AND c.Weight = t.Weight AND c.Height = t.Height