oracle表中重复的总数

Question

我有一张如下表

SUBJECT Years MARKS
AB      1       20
AB      1       25
AC      1       20
AC      1       30
AC      1       40
AD      1       20

我只需要重复数(主题||年),预期答案是2而不是

AB1 -- 2
AC1 -- 3

Answer 1

这将是重复查询之上的另一个查询...

select subject, year, count(*)
  from table1
  group by subject, year
  having count(*) > 1

将为您提供所有结果.另一个指望...

select count(*)
  from (
select subject, year, count(*)
  from table1
  group by subject, year
  having count(*) > 1
) 

应该给你一个或多个重复记录的数量.