MySql对两个表中的记录求和，并与第三个表联接

Question

I have 3 tables. Table A stores stock and category relationship. Add date indicates when the stock was added to the category and remove date means the day which the stock was removed. if remove date is null , it means the stock is still in the category.

      +---+----------+  ------- +------------+------------+
      |id | Stock_id |Category  | Add Date   | Remove Date|
      +---+----------+--------  +------------+------------+
      | 1 |        1 | CategoryA| 2017-09-03 | 2017-09-07 |
      | 2 |        1 | CategoryA|2017-09-11  | null       |
      | 3 |        2 | CategoryA| 2017-09-06 | null |
      +---+----------+--------  +------------+------------+

Table B stores stock transaction amount by days.

  +---+------------+----------+-------------+
  |id | Stock_id   | amount   |  Date       |
  +---+------------+----------+-------------+
  | 1 |          1 |      100 | 2017-09-04  |
  | 2 |          1 |      100 | 2017-09-05  |
  | 3 |          1 |      100 | 2017-09-06  |
  | 4 |          1 |      100 | 2017-09-07  |
  | 5 |          1 |      100 | 2017-09-08  |
  | 6 |          1 |      100 | 2017-09-09  |
  | 7 |          2 |      100 | 2017-09-05  |
  | 8 |          2 |      200 | 2017-09-06  |
   ....
  | 2 |          2 |      200 | 2017-09-10  |
  +---+------------+----------+-------------+

Table C stores category transaction amount by days.

  +---+------------+----------+-------------+
  |id | Category   | amount   |  Date       |
  +---+------------+----------+-------------+
  | 1 |          A |      300 | 2017-09-04  |
  | 2 |          A |      300 | 2017-09-05  |
  | 3 |          A |      300 | 2017-09-06  |
  | 4 |          A |      300 | 2017-09-07  |
  | 5 |          A |      300 | 2017-09-08  |
  +---+------------+----------+-------------+

What I want to do is in a given period, such as from 2017-09-04 to 2017-09-08, 1)sum the category amount in the period, 2)and then sum all the stock's amount by id which is in the category in the period. 3) the divide the 2 by 1 to calculate the ratio. for STOCK ID1, for it was removed on 09-07, sql should only calculate it's amount for 3 days records(09-03/09.06). for STOCK ID2, it was added on 09-06, sql should only calculate it's amount for 3 days from 09.06 to 09.08. The sum amount for category in Table C is simple, just sum 5 days. The result What I expect is

  +---+----------+  ------- +
  |id | Stockid  |Result    |
  +---+----------+--------  +
  | 1 |        1 | 0.2      |     # (100+100+100)/300*5            
  | 2 |        2 | 0.4      |     # (200+200+200)/300*5

How can I do it? Thank you all!

Answer 1

I found the code example a bit tricky to follow but here's an attempt. Note that although this may not solve your problem directly, hopefully you will be able to apply the approach in general to solve your issue.

CREATE TABLE tableA(id INT, stockId INT, category CHAR(1), addDate DATE, removeDate DATE);

INSERT INTO tableA VALUES
  (1, 1, 'A', '2017-09-03', '2017-09-07'),
  (2, 1, 'A', '2017-09-11', null),
  (3, 2, 'A', '2017-09-06', null);

CREATE TABLE tableB(id INT, stockId INT, amount INT, `date` DATE);

INSERT INTO tableB VALUES
  (1, 1, 100, '2017-09-04'),
  (2, 1, 100, '2017-09-05'),
  (3, 1, 100, '2017-09-06'),
  (4, 1, 100, '2017-09-07'),
  (5, 1, 100, '2017-09-08'),
  (6, 1, 100, '2017-09-09'),
  (7, 2, 100, '2017-09-05'),
  (8, 2, 200, '2017-09-06'),
  (9, 2, 200, '2017-09-06'),
  (10, 2, 200, '2017-09-10');

CREATE TABLE tableC (id INT, category CHAR(1), amount INT, `date` DATE);

INSERT INTO tableC VALUES
  (1, 'A', 300, '2017-09-04'),
  (2, 'A', 300, '2017-09-05'),
  (3, 'A', 300, '2017-09-06'),
  (4, 'A', 300, '2017-09-07'),
  (5, 'A', 300, '2017-09-08');

SELECT table_AB.tableAB_SUM / table_B.tableB_SUM * TIMESTAMPDIFF(DAY, '2017-09-04', '2017-09-08') FROM  
    (
    SELECT tableB.stockId, SUM(tableB.amount) tableAB_SUM FROM 
        tableB
    LEFT OUTER JOIN
        tableA
    ON tableB.stockId = tableA.stockId
    WHERE tableB.`date` BETWEEN '2017-09-04' AND '2017-09-08' AND (NOT tableA.addDate > '2017-09-08' OR NOT IFNULL(tableA.removeDate, CURDATE()) < '2017-09-08')
    GROUP BY tableA.stockId
    ) table_AB
LEFT OUTER JOIN
    (
    SELECT stockId, SUM(amount) tableB_SUM FROM tableB WHERE `date` BETWEEN '2017-09-04' AND '2017-09-08' GROUP BY stockId
    ) table_B
ON table_AB.stockID = table_B.stockID;

Let me know if anythings unclear.

Regards,

James