Where Clause In Sub-query

Following SQL query: select * from er_101 where cd_relnaam IN ( select cd_relnaam from er_101 group by cd_relnaam having count(*) > 1) AND ld_relopdra

Solution 1:

You can also use WHERE in sub-query.

SELECT*FROM er_101
 WHERE cd_relnaam IN ( 
     SELECT cd_relnaam 
     FROM er_101 
     WHERE ld_relopdrachtgever ='1'<--You can add WHERE clause before GROUP BY--^^^^^----GROUPBY cd_relnaam 
     HAVINGCOUNT(*) >1)
 AND ld_relopdrachtgever ='1'

Solution 2:

see this "article" about finding duplicate records http://blog.sqlauthority.com/2007/07/11/sql-server-count-duplicate-records-rows/