WHERE clause in sub-query

Question

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_relopdrachtgever = '1'

Though I need to have that sub query also limits on ld_relopdrachtgever = '1'
How is that possible with an HAVING statement?

Answer 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
   --^^^^^----
     GROUP BY cd_relnaam 
     HAVING COUNT(*) > 1)
 AND ld_relopdrachtgever = '1'

Answer 2

看到关于查找重复记录的“文章” http://blog.sqlauthority.com/2007/07/11/sql-server-count-duplicate-records-rows/