Question

我有一张表history，它包含一个因子及其更改的时间戳以及它所属的区域，如下所示：

zone_id | validity_period_start | factor
--------+-----------------------+-------
 1      | 1970-01-01            | 50
 1      | 2000-03-03            | 70
 2      | 2000-02-02            | 90
 3      | 2005-08-08            | 20
 3      | 2010-10-10            | 30

我还有另一张表report，其中包含日期类似区域的报告：

report_date | zone_id | value
------------+---------+------
2005-09-09  | 1       | 500
2005-09-09  | 2       | 300
2005-09-09  | 3       | 200
2005-09-10  | 1       | 600
2005-09-10  | 2       | 700
2005-09-10  | 3       | 900

现在我想做一个 SELECT * FROM report WHERE report_date BETWEEN ( "2005-09-09" AND "2005-09-10") 和JOIN history。我希望得到价值，理想情况是返回表格中的product = value*factor基于history.factor有效的report.report_date，如下所示：

 report_date | zone_id | value | factor | product |
 ------------+---------+-------+--------+---------+ 
 2005-09-09  | 1       | 500   | 70     | 35000   |
 2005-09-09  | 2       | 300   | 90     | 27000   |
 2005-09-09  | 3       | 200   | 20     | 4000    |
 2005-09-10  | 1       | 600   | 70     | 42000   |
 2005-09-10  | 2       | 700   | 90     | 63000   |
 2005-09-10  | 3       | 900   | 20     | 18000   |

为了您的谨慎，示例创建代码：

CREATE TABLE rikai_history
(zone_id INT, validity_period_start DATE, factor INT);
INSERT INTO rikai_history VALUES
(1, "1970-01-01", 50),
(1, "2000-03-03", 70),
(2, "2000-02-02", 90),
(3, "2005-08-08", 20),
(3, "2010-10-10", 30);

CREATE TABLE rikai_report
(report_date DATE, zone_id INT, value INT);
INSERT INTO rikai_report VALUES
("2005-09-09", 1, 500),
("2005-09-09", 2, 300),
("2005-09-09", 3, 200),
("2005-09-10", 1, 600),
("2005-09-10", 2, 700),
("2005-09-10", 3, 900);

Answer 1

假设在（zone_id，validity_period_start）和（zone_id，report_date）上形成PRIMARY KEY ......

SELECT x.report_date
     , x.zone_id
     , x.value
     , y.factor
     , x.value*y.factor product 
  FROM 
     ( SELECT r.*
            , MAX(validity_period_start) max_start 
         FROM rikai_report r 
         JOIN rikai_history h 
           ON h.zone_id = r.zone_id
          AND h.validity_period_start <= r.report_date 
        GROUP 
           BY r.report_date,r.zone_id
      ) x 
   JOIN rikai_history y 
     ON y.zone_id = x.zone_id 
    AND y.validity_period_start = x.max_start ;

如何查询“历史”表以查找在某个特定日期对于连接有效的值

1 个答案: