子查询 - case when - subselect - group by - count答案

【问题标题】：Subquery - case when - subselect - group by - count子查询 - case when - subselect - group by - count
【发布时间】：2021-12-22 07:00:17
【问题描述】：

给定 2 张桌子，我需要一个购物奖励的分组摘要。更多的项目意味着更多的奖励。

tab_basket

id	name	shopping_no	type
001	Mike	00001	A
002	Mike	00001	A
003	Mike	00001	A
004	Tom	00002	B
005	Tom	00002	B
006	Tony	00003	A
007	Heinz	00004	A

tab_award

items	award	type_award
1	0.05	A
2	0.50	A
3	0.90	A
4	1.00	A
1	0.15	B
2	0.70	B
3	1.10	B
4	1.30	B

我需要下表作为结果。

award	items	shopping_no	type _award
0.90	3	00001	A
0.70	2	00002	B
0.05	1	00003	A
0.05	1	00004	A

我的解决方案尝试。我每次只得到 null 作为奖励的结果（else 结果）或错误“sql0811 result of select more one row”。我很乐意为您提供任何帮助，谢谢！

SELECT          award,
                items,
                shopping_no,
                type_award
FROM            tab_basket t
LEFT OUTER JOIN tab_award u ON t.TYPE = u.type_award
                           AND CASE WHEN (SELECT COUNT(shopping_no)
                                            FROM tab_basket m
                                           WHERE t.id = m.id
                                             AND t.name = m.name
                                             AND t.shopping_no = m.shopping_no
                                             AND t.TYPE = u.TYPE
                                           GROUP BY shopping_no ) = '1' THEN '1'
                               case WHEN (SELECT COUNT(shopping_no)
                                            FROM tab_basket m
                                           WHERE t.id = m.id
                                             AND t.name = m.name
                                             AND t.shopping_no = m.shopping_no
                                             AND t.TYPE = u.TYPE
                                           GROUP BY shopping_no ) = '2' THEN '2' 
                               CASE WHEN (SELECT COUNT(shopping_no)
                                            FROM tab_basket m
                                           WHERE t.id = m.id
                                             AND t.name = m.name
                                             AND t.shopping_no = m.shopping_no
                                             AND t.TYPE = u.TYPE                                                                                                                  
                                           GROUP BY shopping_no ) = '3' THEN '3'
                               CASE WHEN (SELECT COUNT(shopping_no)
                                            FROM tab_basket m
                                           WHERE t.id = m.id
                                             AND t.name = m.name                                                                                                                   
                                             AND t.shopping_no = m.shopping_no                                                                                                                                 
                                             AND t.TYPE = u.TYPE                                                                                                                    
                                           GROUP BY shopping_no ) = '4' THEN '4'
                               ELSE 'no_price'                                                                                                   
                                END = u.award

【问题讨论】：

标签： sql db2

【解决方案1】：

您可以先聚合您的 tab_basket 表，然后可以将其与 tab_award 表连接 -

SELECT TB.award, TB.items, TA.shopping_no, TB.type_award
  FROM (SELECT name, shopping_no, type, COUNT(*) CNT
          FROM tab_basket
         GROUP BY name, shopping_no, type) TB
  JOIN tab_award TA ON TB.type = TA.type_award
                    AND TB.CNT = TA.items

【讨论】：