SQL在特定日期选择重复项

Question

I'm trying to find duplicate entries which occurred on the same day. I have a database table which basically consists only from ID, USERNAME and DATE_CREATED.

I need a select which does roughly this:

SELECT USERNAME,DATE_CREATED 
FROM THE_TABLE WHERE {more than one USERNAME exists on date TRUNC(DATE_CREATED)}

Is it possible to do it without creating a procedure only by SELECT? Thanks for advice.

Answer 1

SELECT  USERNAME, TRUNC(DATE_CREATED)
FROM    THE_TABLE
GROUP   BY
        USERNAME, TRUNC(DATE_CREATED)
HAVING  COUNT(*) > 1;

Example:

SELECT  USERNAME, TRUNC(DATE_CREATED)
FROM    
(
        SELECT  'a' username, sysdate date_created from dual union all
        SELECT  'a' username, sysdate date_created from dual union all
        SELECT  'b' username, sysdate date_created from dual union all
        SELECT  'b' username, sysdate date_created from dual
)
GROUP   BY
        USERNAME, TRUNC(DATE_CREATED)
HAVING  COUNT(*) > 1;
/*
a   2013-06-18 00:00:00
b   2013-06-18 00:00:00
*/

To get the full date in the output it is slightly complicated:

SELECT  DISTINCT
        username
,       date_created
FROM    the_table ot
WHERE   EXISTS
        (
            SELECT  1
            FROM    the_table it
            WHERE   TRUNC(ot.date_created) = TRUNC(it.date_created)
            AND     ot.username            = it.username
            GROUP   BY
                    USERNAME, TRUNC(DATE_CREATED)
            HAVING  COUNT(*) > 1
        )
;
/*
a   2013-06-18 12:48:40
b   2013-06-18 12:48:40
*/

Table has to be accessed twice + DISTINCT keyword is required. Yes, the performance can decrease.

Answer 2

This will return the full date in the output.

SELECT 
      USERNAME
    , DATE_CREATED 
FROM 
(
  SELECT 
       USERNAME
    ,  DATE_CREATED
    ,  COUNT( *) over ( PARTITION by USERNAME, TRUNC( DATE_CREATED, 'DD') ) cnt
  FROM THE_TABLE
)
WHERE cnt > 1
;

Answer 3

SELECT USERNAME, trunc(DATE_CREATED)
FROM THE_TABLE 
group by Username,TRUNC(DATE_CREATED)
having count(1) > 1

Answer 4

Use Having

select USERNAME, DATE_CREATED 
from test
group by USERNAME, DATE_CREATED 
Having COUNT(1) > 1