show duplicate records

Question

I have this query

SELECT  id, timeOrdered, order_desc, firstname, lastname
FROM `db`.`myTable` 
WHERE `myTable`.`customer_number` IN (100, 101, 102, 103, 104, 105)

I am trying to find which are duplicate records. If the timeOrdered, order_desc, firstname, lastname are same then its dupe.

What would be the query for that
Thanks

Answer 1

To see what values have duplicates:

  SELECT t.order_desc, 
         t.firstname,
         t.lastname
    FROM db.mytable t
   WHERE t.customer_number IN (100, 101, 102, 103, 104, 105)
GROUP BY t.order_desc, t.firstname, t.lastname, t.timeordered
  HAVING COUNT(*) > 1

To see the entire record associated with those duplicates:

SELECT x.*
  FROM db.mytable x
  WHERE EXISTS(SELECT NULL
                 FROM db.mytable t
                WHERE t.customer_number IN (100, 101, 102, 103, 104, 105)
                  AND t.order_desc = x.order_desc
                  AND t.firstname = x.firstname
                  AND t.lastname = x.lastname
                  AND t.timeordered = x.timeordered
             GROUP BY t.order_desc, t.firstname, t.lastname, t.timeordered
               HAVING COUNT(*) > 1) 
 WHERE x.customer_number IN (100, 101, 102, 103, 104, 105)

Answer 2

SELECT DISTINCT
    t1.id
FROM 
    mytable t1
    INNER JOIN mytable t2 ON 
        t1.timeordered = t2.timeordered AND
        t1.order_desc = t2.order_desc AND
        t1.firstname = t2.firstname AND
        t1.lastname = t2.lastname AND
        t1.id <> t2.id