WHERE clause in sub-query

问题

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?

回答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'

回答2:

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

来源：https://stackoverflow.com/questions/13085483/where-clause-in-sub-query