Question

我有两个表，名为t_header和t_detail。

此数据标题

ID | doc_num | promotion
1     0001      0
2     0002      1

此数据详情

ID | doc_num | item | price
1     0001      2      100
2     0001      3      170
3     0001      4      102
4     0001      5      105
5     0002      3      120
6     0002      4       99
7     0002      7      165

如果促销= 1，那么价格详细将采取详细的数据促销价格，对于上表，如果item = 3然后将价格= 120，因为具有doc_num 002 promo = 1的项目，如果没有促销它将采用价格docnum 001,001 num doc标准价格和逐项

输出

ID | doc_num | item | price | promotion
1     0001      2      100    0
5     0002      3      120    1
6     0002      4      99     1
4     0001      5      105    0
7     0002      7      165    0

Answer 1

我猜您需要选择促销价格，否则您需要正常价格。因此，您应该在LEFT JOIN之后使用IF语句选择列。此查询可能有所帮助：

SELECT
if(td_prom.ID, td_prom.ID, td_norm.ID) as ID, 
th.doc_num,
if(td_prom.price, td_prom.price, td_norm.price) as price,
if(td_prom.item, td_prom.item, td_norm.item) as item,
th.promo
FROM
t_header th
LEFT JOIN t_detail as td_norm ON th.doc_num = td_norm.doc_num AND th.promo = 0
LEFT JOIN t_detail as td_prom ON th.doc_num = td_prom.doc_num AND th.promo = 1
GROUP BY item

Answer 2

正如我在您想要的结果中看到的那样，您不希望项目显示两次。在此旁边，我假设您的数据库中有一个项目表。然后我提出了这个问题。第一部分是提取促销中的项目。第二部分仅添加不在促销中的项目，但不包括在其上有促销的项目。

SELECT d.id, d.doc_num, d.item, d.price, h.promo
FROM items AS i
  INNER JOIN detail AS d ON i.id = d.id
  INNER JOIN header AS h ON h.doc_num = d.doc_num AND h.promo = 1
UNION ALL
SELECT nopromo.*
FROM (SELECT d.id, d.doc_num, d.item, d.price, h.promo
      FROM items AS i
        INNER JOIN detail AS d ON i.id = d.id
        INNER JOIN header AS h ON h.doc_num = d.doc_num AND h.promo = 0) AS nopromo
  LEFT OUTER JOIN
    (SELECT d.id, d.doc_num, d.item, d.price, h.promo
     FROM item AS i
       INNER JOIN detail AS d ON i.id = d.id
       INNER JOIN header AS h ON h.doc_num = d.doc_num AND h.promo = 1) AS ipromo
  ON nopromo.item = ipromo.item
WHERE ipromo.id IS NULL
ORDER BY item

结果

+---+--------+-----+------+------+
|id |doc_num |item |price |promo |
+---+--------+-----+------+------+
|1  |0001    |2    |100   |0     |
|5  |0002    |3    |120   |1     |
|6  |0002    |4    |99    |1     |
|4  |0001    |5    |105   |0     |
|7  |0002    |7    |165   |1     |
+---+--------+-----+------+------+

选择数据头连接细节最后doc_num头是促销？

2 个答案: