sql - 子查询中的 WHERE 子句

Question

以下 SQL 查询：

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'

虽然我需要那个子查询也限制ld_relopdrachtgever = '1'
了 HAVING 语句怎么可能？

Answer 1

您也可以WHERE在子查询中使用。

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

请参阅有关查找重复记录的“文章” http://blog.sqlauthority.com/2007/07/11/sql-server-count-duplicate-records-rows/