Question

I want to get the count how many values are repeating in the result in a column in result of a query.

The result set I am getting from a complex query is –

svn rvn eng     count(*)
1   1   Boy            1
2   1   Teacher        1
3   1   Chair          1
3   2   Chairwoman      1
3   3   Chairperson     1
4   1   Without         1
4   2   Without fail    1
5   1   Anyone          1
5   2   Anyone else     1
6   1   Permission      1

I just want to get the number of duplicate values in SVN coloumn in fourth coloumn.

i.e.

svn rvn eng     count(*)
1   1   Boy            1
2   1   Teacher        1

3   1   Chair          3
3   2   Chairwoman      3
3   3   Chairperson     3

4   1   Without         2
4   2   Without fail    2

5   1   Anyone          2
5   2   Anyone else     2
6   1   Permission      1

Please Help me out on this, Also please tell me what effect this can cause on the efficiency on the query??

*Note – * I want the count of the values that are picked up in the result set.
there are more entries with svn 1,2,4,6 in the table. but count only how many has been selected.

Thanks in advance 🙂

EDIT1

Here is my current query :-

SELECT `svn` , `rvn` ,`eng` , count(*) FROM 
        (SELECT `svn`, `rvn`, `eng`, `hin` 
              FROM `table1` 
              WHERE `SN` = @sn
            UNION DISTINCT
            SELECT `table1_refer`.`sn_svn` AS 'svn',  
                           `table1`.`rvn`, `table1`.`eng` ,  
                          `vocab_rel`.`hin`
            FROM  `table1` 
            JOIN  `table1_refer` 
            WHERE  `table1_refer`.`rSN` =  `table1`.`SN` 
            AND  `table1_refer`.`svn` =  `table1`.`svn` 
            AND `table1_refer`.`SN` = @sn
        ) AS SUBQUERY
        GROUP BY `svn`,`rvn`
        ORDER BY `svn`, `rvn`

Answer 1

You can use a correlated subquery inside your current complex query to do this like so:

SELECT
  svn, 
  rvn,
  eng,
  (SELECT count(t2.svn)
   FROM Tablename t2
   WHERE t2.svn = t1.svn
  ) AS Count
FROM Tablename t1
....

SQL Fiddle Demo

This will give you:

| SVN | RVN |         ENG | COUNT |
-----------------------------------
|   1 |   1 |         Boy |     1 |
|   2 |   1 |     Teacher |     1 |
|   3 |   1 |       Chair |     3 |
|   3 |   2 |  Chairwoman |     3 |
|   3 |   3 | Chairperson |     3 |
|   4 |   1 |     Without |     2 |
|   4 |   2 | Withoutfail |     2 |
|   5 |   1 |      Anyone |     2 |
|   5 |   2 |  Anyoneelse |     2 |
|   6 |   1 |  Permission |     1 |