Question

我想象的结果如下：

Category | Year |  sum  |
--------- ------ --------
    A      2008    200
    A      2009      0
    B      2008    100
    B      2009      5
   ...     ...     ...

即。每年和类的交易的总和。

有些情况下，类别一年内没有任何交易。在这些情况下，结果的第二行不会出现。我如何重新编写上述查询以便为每个类别包含2008,2009？

select category, to_char(trans_date, 'YYYY') year, sum(trans_value)
from transaction
group by category, to_char(trans_date, 'YYYY')
order by 1, 2;

Answer 1

理想情况下，您需要一个类别表和年份表：

select c.category, y.year, nvl(sum(t.trans_value),0)
from categories c
cross join years y
left outer join transaction t
   on  to_char(t.trans_date, 'YYYY') = y.year
   and t.category = c.category
group by c.category, y.year
order by 1, 2;

希望你有一个类别表，但你可能没有多年的表，在这种情况下你可以“伪造”这样的一个：

with years as
( select 2007+rownum year
  from dual
  connect by rownum < 10) -- returns 2008, 2009, ..., 2017
select c.category, y.year, nvl(sum(t.trans_value),0)
from categories c
cross join years y
left outer join transaction t
   on  to_char(t.trans_date, 'YYYY') = y.year
   and t.category = c.category
group by c.category, y.year
order by 1, 2;

Answer 2

使用partitioned outer join，您不需要类别表。

我使用了与“dcp”相同的交易表：

SQL> create table transactions
  2  ( category varchar(1)
  3  , trans_date date
  4  , trans_value number(25,8)
  5  );

Table created.

SQL> insert into transactions values ('A',to_date('2008-01-01','yyyy-mm-dd'),100.0);

1 row created.

SQL> insert into transactions values ('A',to_date('2008-02-01','yyyy-mm-dd'),100.0);

1 row created.

SQL> insert into transactions values ('B',to_date('2008-01-01','yyyy-mm-dd'),50.0);

1 row created.

SQL> insert into transactions values ('B',to_date('2008-02-01','yyyy-mm-dd'),50.0);

1 row created.

SQL> insert into transactions values ('B',to_date('2009-08-01','yyyy-mm-dd'),5.0);

1 row created.

对于分区外连接，您只需要一组年份来对外连接进行分区。在下面的查询中，我使用了2年（2008年和2009年），但您可以轻松调整该设置。

SQL> with the_years as
  2  ( select 2007 + level year
  3         , trunc(to_date(2007 + level,'yyyy'),'yy') start_of_year
  4         , trunc(to_date(2007 + level + 1,'yyyy'),'yy') - interval '1' second end_of_year
  5      from dual
  6   connect by level <= 2
  7  )
  8  select t.category                "Category"
  9       , y.year                    "Year"
 10       , nvl(sum(t.trans_value),0) "sum"
 11    from the_years y
 12         left outer join transactions t
 13           partition by (t.category)
 14           on (t.trans_date between y.start_of_year and y.end_of_year)
 15   group by t.category
 16       , y.year
 17   order by t.category
 18       , y.year
 19  /

Category       Year        sum
-------- ---------- ----------
A              2008        200
A              2009          0
B              2008        100
B              2009          5

4 rows selected.

另请注意，我使用了start_of_year和end_of_year，因此如果要对trans_date进行过滤并且您在该列上有索引，则可以使用它。另一个选择是简单地使用trunc（t.trans_date）= y.year作为条件。

希望这有帮助。

的问候，
罗布。

Answer 3

这是一个完整的，有效的例子：

CREATE TABLE transactions (CATEGORY VARCHAR(1), trans_date DATE, trans_value NUMBER(25,8));
CREATE TABLE YEAR (YEAR NUMBER(4));

CREATE TABLE categories (CATEGORY VARCHAR(1));
INSERT INTO categories VALUES ('A');
INSERT INTO categories VALUES ('B');

INSERT INTO transactions VALUES ('A',to_date('2008-01-01','YYYY-MM-DD'),100.0);
INSERT INTO transactions VALUES ('A',to_date('2008-02-01','YYYY-MM-DD'),100.0);

INSERT INTO transactions VALUES ('B',to_date('2008-01-01','YYYY-MM-DD'),50.0);
INSERT INTO transactions VALUES ('B',to_date('2008-02-01','YYYY-MM-DD'),50.0);

INSERT INTO transactions VALUES ('B',to_date('2009-08-01','YYYY-MM-DD'),5.0);

INSERT INTO YEAR VALUES (2008);
INSERT INTO YEAR VALUES (2009);


SELECT b.category
     , b.year
     , SUM(nvl(a.trans_value,0))
  FROM (SELECT to_char(a.trans_date,'YYYY') YEAR
             , CATEGORY
             , SUM(NVL(trans_value,0)) trans_value
          FROM transactions a
        GROUP BY to_char(a.trans_date,'YYYY')
               , a.category ) a
     , (SELECT
        DISTINCT a.category
               , b.year
          FROM   categories a
             ,   YEAR b ) b
 WHERE b.year = to_char(a.year(+))
   AND b.category = a.category(+)
 GROUP BY
       b.category
     , b.year  
 ORDER BY 1
         ,2;

输出：

    CATEGORY    YEAR    SUM(NVL(A.TRANS_VALUE,0))
1   A           2008    200
2   A           2009    0
3   B           2008    100
4   B           2009    5

如何按类别划分年份，以便每个类别每年包含零金额？

3 个答案: