Question

请协助以下事项：我在数据库INFO中有2个表PurchaseO和SalesO。

购买O：

ITEMNO    DATE       QTY
A         20180701   5
A         20180702   2
A         20180703   1
B         20180701   2
C         20180704   3

SalesO：

ITEMNO    DATE       QTY
A         20180701   5
A         20180704   4   
B         20180702   2
C         20180704   3

如何在DATE之前将这两个表联接起来以获得以下结果：

ITEMNO    DATE       PurchaseQTY   SalesQTY
A         20180701   5             5
A         20180702   2
A         20180703   1
A         20180704                 4
B         20180701   2
B         20180702                 2
C         20180704   3             3

Answer 1

一种方法是full join：

select coalesce(p.itemno, s.itemno) as itemno,
       coalesce(p.date, s.date) as date,
       p.qty as purchase_qty,
       s.qty as sales_qty
from purchases p full join
     sales s
     on p.itemno = s.itemno and p.date = s.date;

如果任一表中给定项目的日期都有重复，并且您想累加数量，那么union all / group by是更好的方法：

select itemno, date,
       sum(purchase_qty) as purchase_qty,
       sum(sales_qty) as sales_qty
from ((select p.itemno, p.date, sum(p.qty) as purchase_qty, 0 as sales_qty
       from purchases p
       group by p.itemno, p.date
      ) union all
      (select s.itemno, s.date, 0, sum(s.qty) as sales_qty
       from purchases p
       group by p.itemno, p.date
      )
     ) sp
group by itemno, date;

Answer 2

您可以像加入ID一样加入日期

SELECT
  po.ITEMNO,
  so.[DATE],
  po.QTY AS [PurchaseQTY],
  so.QTY AS [SalesQTY]
FROM
  PurchasesO AS po
FULL JOIN
  SalesO AS so
ON
  so.ITEMNO = po.ITEMNO AND
  so.[DATE] = po.[DATE]

如何基于日期联接多个表中的值

2 个答案: