Question

i have a table with id, first, last and i want to run a query that says

give me every record where the combination of first and last exists more than once

(i am trying to find duplicate records)

Answer 1

EDIT

Concatenation will give out false answers as pointed out in the comments (‘Roberto Neil’ vs ‘Robert ONeil’.

Here is an answer that eliminates the concatenation issue. I found out the non duplicates and eliminated them from the final answer.

WITH MyTable AS
(
    SELECT 1 as ID, 'John' as FirstName, 'Doe' as LastName
    UNION
    SELECT 2 as ID, 'John' as FirstName, 'Doe' as LastName
    UNION
    SELECT 3 as ID, 'Tim' as FirstName, 'Doe' as LastName
    UNION
    SELECT 4 as ID, 'Jane' as FirstName, 'Doe' as LastName
    UNION
    SELECT 5 as ID, 'Jane' as FirstName, 'Doe' as LastName
)
SELECT Id, FirstName, LastName
FROM MyTable SelectTable
WHERE Id Not In
(
    SELECT Min (Id)
    From MyTable SearchTable
    GROUP BY FirstName, LastName
    HAVING COUNT (*) = 1
)

---

OLD SOLUTION

Use GROUP BY and HAVING.. check out this working sample

WITH MyTable AS
(
SELECT 1 as ID, 'John' as FirstName, 'Doe' as LastName
UNION
SELECT 2 as ID, 'John' as FirstName, 'Doe' as LastName
UNION
SELECT 3 as ID, 'Time' as FirstName, 'Doe' as LastName
UNION
SELECT 4 as ID, 'Jane' as FirstName, 'Doe' as LastName
)
SELECT ID, FirstName, LastName
FROM MyTable
WHERE FirstName + LastName IN
(
    SELECT FirstName + LastName
    FROM MyTable
    GROUP BY FirstName + LastName
    HAVING COUNT (*) > 1
)

This will result in the following

ID          FirstName LastName
----------- --------- --------
1           John      Doe
2           John      Doe