选读SQL经典实例笔记13_case与聚合

1. 识别非小计行

1.1. 结果集


1.2. DB2

1.3. Oracle

1.4. 超级聚合(supera ggregate)值

1.4.1. sql

select deptno, job, sum(sal) sal,
       grouping(deptno) deptno_subtotals,
       grouping(job) job_subtotals
  from emp
 group by cube(deptno,job)

1.5. SQL Server

1.5.1.  sql

select deptno, job, sum(sal) sal,
        grouping(deptno) deptno_subtotals,
        grouping(job) job_subtotals
   from emp
  group by deptno,job with cube

2. 使用CASE表达式标记行数据

2.1. 结果集

2.2. sql

select ename,
       case when job = 'CLERK'
            then 1 else 0
       end as is_clerk,
       case when job = 'SALESMAN'
            then 1 else 0
       end as is_sales,
       case when job = 'MANAGER'
            then 1 else 0
       end as is_mgr,
       case when job = 'ANALYST'
            then 1 else 0
       end as is_analyst,
       case when job = 'PRESIDENT'
            then 1 else 0
       end as is_prez
  from emp
 order by 2,3,4,5,6

3. 创建稀疏矩阵

3.1. 结果集

3.2. sql

select case deptno when 10 then ename end as d10,
       case deptno when 20 then ename end as d20,
       case deptno when 30 then ename end as d30,
       case job when 'CLERK'     then ename end as clerks,
       case job when 'MANAGER'   then ename end as mgrs,
       case job when 'PRESIDENT' then ename end as prez,
       case job when 'ANALYST'   then ename end as anals,
       case job when 'SALESMAN'  then ename end as sales
  from emp

3.3. sql

select max(case deptno when 10 then ename end) d10,
       max(case deptno when 20 then ename end) d20,
       max(case deptno when 30 then ename end) d30,
       max(case job when 'CLERK'     then ename end) clerks,
       max(case job when 'MANAGER'   then ename end) mgrs,
       max(case job when 'PRESIDENT' then ename end) prez,
       max(case job when 'ANALYST'   then ename end) anals,
       max(case job when 'SALESMAN' then ename end) sales
  from (
select deptno, job, ename,
       row_number()over(partition by deptno order by empno) rn
  from emp
       ) x
 group by rn

3.3.1. 删除一些Null行,以便让整个报表显得“紧密”一些

4. 按照时间单位分组

4.1. 结果集

4.1.1. sql

select trx_id,
       trx_date,
       trx_cnt
  from trx_log
TRX_ID TRX_DATE                TRX_CNT
------ -------------------- ----------
     1 28-JUL-2005 19:03:07         44
     2 28-JUL-2005 19:03:08         18
     3 28-JUL-2005 19:03:09         23
     4 28-JUL-2005 19:03:10         29
     5 28-JUL-2005 19:03:11         27
     6 28-JUL-2005 19:03:12         45
     7 28-JUL-2005 19:03:13         45
     8 28-JUL-2005 19:03:14         32
     9 28-JUL-2005 19:03:15         41
    10 28-JUL-2005 19:03:16         15
    11 28-JUL-2005 19:03:17         24
    12 28-JUL-2005 19:03:18         47
    13 28-JUL-2005 19:03:19         37
    14 28-JUL-2005 19:03:20         48
    15 28-JUL-2005 19:03:21         46
    16 28-JUL-2005 19:03:22         44
    17 28-JUL-2005 19:03:23         36
    18 28-JUL-2005 19:03:24         41
    19 28-JUL-2005 19:03:25         33
    20 28-JUL-2005 19:03:26         19

4.1.2. 结果集

 GRP TRX_START            TRX_END                   TOTAL
--- -------------------- -------------------- ----------
  1 28-JUL-2005 19:03:07 28-JUL-2005 19:03:11        141
  2 28-JUL-2005 19:03:12 28-JUL-2005 19:03:16        178
  3 28-JUL-2005 19:03:17 28-JUL-2005 19:03:21        202
  4 28-JUL-2005 19:03:22 28-JUL-2005 19:03:26        173

4.2. sql

select ceil(trx_id/5.0) as grp,
       min(trx_date)    as trx_start,
       max(trx_date)    as trx_end,
       sum(trx_cnt)     as total
  from trx_log
 group by ceil(trx_id/5.0)

5. 多维度聚合运算

5.1. 结果集

5.2. DB2

5.3. Oracle

5.4. SQL Server

5.5. 窗口函数COUNT OVER

5.5.1. sql

select ename,
       deptno,
       count(*)over(partition by deptno) deptno_cnt,
       job,
       count(*)over(partition by job) job_cnt,
       count(*)over() total
  from emp

5.6. PostgreSQL

5.7. MySQL

5.8. 使用标量子查询

5.8.1. sql

select e.ename,
       e.deptno,
       (select count(*) from emp d
         where d.deptno = e.deptno) as deptno_cnt,
       job,
       (select count(*) from emp d
         where d.job = e.job) as job_cnt,
       (select count(*) from emp) as total
  from emp e

6. 动态区间聚合运算

6.1. 入职最早的员工的HIREDATE作为起始点,每隔90天计算一次工资合计值

6.1.1. 结果集

HIREDATE        SAL SPENDING_PATTERN
----------- ------- ----------------
17-DEC-1980     800              800
20-FEB-1981    1600             2400
22-FEB-1981    1250             3650
02-APR-1981    2975             5825
01-MAY-1981    2850             8675
09-JUN-1981    2450             8275
08-SEP-1981    1500             1500
28-SEP-1981    1250             2750
17-NOV-1981    5000             7750
03-DEC-1981     950            11700
03-DEC-1981    3000            11700
23-JAN-1982    1300            10250
09-DEC-1982    3000             3000
12-JAN-1983    1100             4100

6.2. DB2

6.3. Oracle

6.4. 窗口函数SUM OVER

6.4.1. sql

select hiredat,
       sal,
       sum(sal)over(order by days(hiredate)
                       range between 90 preceding
                         and current row) spending_pattern
  from emp e

6.4.2. sql

select hiredate,
       sal,
       sum(sal)over(order by hiredate
                       range between 90 preceding
                         and current row) spending_pattern
  from emp e

6.4.2.1. Oracle的窗口函数支持DATE类型排序

6.5. PostgreSQL

6.6. MySQL

6.7. SQL Server

6.8. 使用标量子查询

6.8.1. sql

select e.hiredate,
       e.sal,
       (select sum(sal) from emp d
         where d.hiredate between e.hiredate-90
                              and e.hiredate) as spending_pattern
  from emp e
 order by 1

7. 变换带有小计的结果集

7.1. 结果集


7.2. DB2

7.3. Oracle

7.4. 使用GROUP BY的ROLLUP扩展

7.4.1.  sql

select mgr,
        sum(case deptno when 10 then sal else 0 end) dept10,
        sum(case deptno when 20 then sal else 0 end) dept20,
        sum(case deptno when 30 then sal else 0 end) dept30,
        sum(case flag when '11' then sal else null end) total
   from (
 select deptno,mgr,sum(sal) sal,
        cast(grouping(deptno) as char(1))||
        cast(grouping(mgr) as char(1)) flag
   from emp
  where mgr is not null
  group by rollup(deptno,mgr)
        ) x
  group by mgr

7.5. SQL Server

7.5.1. sql

select mgr,
       sum(case deptno when 10 then sal else 0 end) dept10,
       sum(case deptno when 20 then sal else 0 end) dept20,
       sum(case deptno when 30 then sal else 0 end) dept30,
       sum(case flag   when '11' then sal else null end) total
  from (
select deptno,mgr,sum(sal) sal,
       cast(grouping(deptno) as char(1))+
       cast(grouping(mgr)    as char(1)) flag
  from emp
 where mgr is not null
 group by deptno,mgr with rollup
       ) x
 group by mgr

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