需求，计算20号部门员工工资出现的次数
使用count() 函数：
SQL> select sal,count(*) time from emp where deptno=20 group by sal;
SAL TIME
---------- ----------
2975 1
1100 1
3000 2
800 1
SQL>
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计算20号部门工资出现的次数，并排出序号
使用dense_rank分析函数
SQL> select sal,dense_rank() over(order by time desc) as seq
2 from
3 (select sal,count(*) time from emp where deptno=20 group by sal) emp;
SAL SEQ
---------- ----------
3000 1
800 2
2975 2
1100 2
SQL>
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根据序号过滤得到序号为2的结果
SQL> select sal
2 from
3 (select sal,dense_rank() over(order by time desc) as seq
4 from
5 (select sal,count(*) time from emp where deptno=20 group by sal) emp) emp
6 where seq=2;
SAL
----------
2975
800
1100
SQL>
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利用partition by 子句分别查询各个部门哪个工资等级的员工多
SQL> select deptno,sal
2 from
3 (select deptno,sal,dense_rank() over(partition by deptno order by time desc) as seq
4 from
5 (select deptno,sal,count(*) time from emp group by deptno,sal) emp ) emp
6 where seq=1;
DEPTNO SAL
---------- ----------
10 5000
10 1300
10 2450
20 3000
30 1250
SQL>
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以上就是计算次数出现最多的次数的方法。
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作者：小花粉的Sanctuary
来源：****
原文：/sungsasong/article/details/78136736
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