Oracle查询和过滤重复数据

对数据库某些意外情况，引起的重复数据，如何处理呢？

----------------查重复：

select *
  from satisfaction_survey s
 where s.as_side = 0
   and s.project_no in (select ss.project_no
                          from satisfaction_survey ss
                         where ss.as_side = 0
                         group by ss.project_no
                        having count(*) > 1)
 order by s.project_no, s.submit_time

思路：从预先选出的数据中（s.as_side = 0），根据特定字段（s.project_no），判断是否存在（count(*) > 1，符合条件的数据不止一条）重复数据

当然，也可以根据多个字段（in 前面的字段，用个括号括起来，in select子句的返回字段对应改变）判断是否存在重复数据

----------------------去重复：

delete from satisfaction_survey s
 where s.as_side = 0
 and(s.project_no/*, to_char(s.submit_time, 'yyyy-mm-dd')*/) in
       (select ss.project_no/*, to_char(ss.submit_time, 'yyyy-mm-dd') */
       from satisfaction_survey ss
       where ss.as_side=0//根据自己实际情况，确定子句（清楚每个sql的结果集很重要）
       group by ss.project_no/*, to_char(ss.submit_time, 'yyyy-mm-dd')*/
      having count(*) > 1)
   and rowid not in
       (select max(rowid) from satisfaction_survey where as_side=0 group by project_no/*, to_char(submit_time, 'yyyy-mm-dd')*/ having count(*) > 1)

思路：在删除全部重复数据时，保留一条（and rowid not in）符合自己需求的数据

这里为了保证程序的健壮性，可以在查询数据时防止查出多条数据，在返回结果外面加一层，只取一条数据：

select *
  from (SELECT ROW_NUMBER() OVER(ORDER BY s.submit_time) 插入时间, s.*
          FROM satisfaction_survey s
         where s.project_no = 'WW-PM-2017-RP-449'
           and s.employee_no = 'BF1019589'
           and s.as_side = 0
           --and s.mark is not null)
           and s.mark is null)
 where 插入时间 = 1

这里根据时间排序，取符合条件的第一条