Oracle：在可空值上分区的分析函数

我不想计算空值。因为NULL不应该等于NULL

查看此查询结果：

---

如果不想筛选出

master

为空的行，可以执行以下操作

选择master， 总和（主值为空时的情况） 然后0 其他1 结束）结束（主分区） 临时工

SQL> ed
Wrote file afiedt.buf

  1  WITH temp as (
  2  SELECT 'A' as master , 1 Col from dual
  3  UNION SELECT 'A' , 3  from dual
  4  UNION SELECT 'B' , 1 from dual
  5  UNION SELECT 'B' , 2 from dual
  6  UNION SELECT 'C' , 1 from dual
  7  UNION SELECT NULL , 1 from dual
  8  UNION SELECT NULL , 2 from dual)
  9  SELECT master,
 10         SUM( CASE WHEN master IS NULL
 11                   THEN 0
 12                   ELSE 1
 13               END) OVER (PARTITION BY master)
 14*   FROM temp
SQL> /

M SUM(CASEWHENMASTERISNULLTHEN0ELSE1END)OVER(PARTITIONBYMASTER)
- -------------------------------------------------------------
A                                                             2
A                                                             2
B                                                             2
B                                                             2
C                                                             1
                                                              0
                                                              0

Null不等于Null。但从聚合的角度来看，null等同于null。并不是分析能做到这一点；这是聚合本身

  1  WITH temp as (
  2  SELECT 'A' as master , 1 Col from dual
  3  UNION SELECT 'A' , 3 from dual
  4  UNION SELECT 'B' , 1 from dual
  5  UNION SELECT 'B' , 2 from dual
  6  UNION SELECT 'C' , 1 from dual
  7  UNION SELECT NULL , 1 from dual
  8  UNION SELECT NULL , 2  from dual )
  9  SELECT
 10     master,
 11     count(Col)
 12  FROM
 13*   temp group by master
SQL> /

M COUNT(COL)
- ----------
           2
A          2
B          2
C          1

---

或者，过滤掉它们：

  1  WITH temp as (
  2  SELECT 'A' as master , 1 Col from dual
  3  UNION SELECT 'A' , 3  from dual
  4  UNION SELECT 'B' , 1 from dual
  5  UNION SELECT 'B' , 2 from dual
  6  UNION SELECT 'C' , 1 from dual
  7  UNION SELECT NULL , 1 from dual
  8  UNION SELECT NULL , 2 from dual)
  9  SELECT
 10     master,
 11     count(Col) over (partition by master)
 12  FROM
 13    temp
 14* WHERE master is not null
SQL> /

M COUNT(COL)OVER(PARTITIONBYMASTER)
- ---------------------------------
A                                 2
A                                 2
B                                 2
B                                 2
C                                 1

---

另外，如果

col

可以为空，并且您也不希望对这些行进行计数，那么

在（按主分区）上进行计数（如果主分区不为空，则col else null end）

注意：

else null

是可选的，如果没有条件匹配，则检测默认值，

case

返回null。如果您不关心

col

是否为null，则只需执行

count（master）over（按master分区）

。而不是Justin的“sum（case…）

  1  WITH temp as (
  2  SELECT 'A' as master , 1 Col from dual
  3  UNION SELECT 'A' , 3  from dual
  4  UNION SELECT 'B' , 1 from dual
  5  UNION SELECT 'B' , 2 from dual
  6  UNION SELECT 'C' , 1 from dual
  7  UNION SELECT NULL , 1 from dual
  8  UNION SELECT NULL , 2 from dual)
  9  SELECT
 10     master,
 11     count(Col) over (partition by master)
 12  FROM
 13    temp
 14* WHERE master is not null
SQL> /

M COUNT(COL)OVER(PARTITIONBYMASTER)
- ---------------------------------
A                                 2
A                                 2
B                                 2
B                                 2
C                                 1