如何左加入，以创建日期范围? [英] How to LEFT JOIN, to create a Date Range?

问题描述

我有这个查询

SELECT userId, orgQuery.timeUnit, 
  @SUM := @SUM + orgQuery.orderValue AS sum, 
  @COUNT := @COUNT + 1 AS count, 
  @AVG := @SUM / @COUNT AS avg
    FROM (
    SELECT userid, orderValue,  
      DATE_FORMAT(`acceptDate`, '%Y%M') AS timeUnit
FROM `agreements` 
    WHERE userId = 4 
    AND acceptDate > 2000-00-00 
   GROUP BY timeUnit
)
AS orgQuery, 
  (SELECT @COUNT := 0, @SUM := 0,@AVG :=0) 
 AS extra GROUP BY timeUnit

输出:

userId  timeUnit    sum count   avg
4         201001    6000    1   6000.0000
4         201003    12000   2   6000.0000
4         201004    19500   3   6500.0000

但是如您所见，某些日期之间有间隔，我希望输出为连续范围，例如:

But as you can see, there is a gap between some dates and I want the output to be a contiguous range eg:

userId  timeUnit    sum count   avg
4         201001    6000    1   6000.0000
4         201002    0       2   3000.0000
4         201003    12000   3   6000.0000
4         201004    19500   4   4875.0000

此查询

(SELECT DATE_FORMAT(`acceptDate`, '%Y%M') AS timeUnit FROM `agreements` GROUP BY timeUnit )

输出完整的日期范围，但是当我尝试左联接两个查询时，count和avg都搞砸了.如何获得想要的结果?

Outputs the full date range, but when I try to LEFT JOIN the two Querys, the count and avg gets all messed up. How can I get the result am looking for?

推荐答案

假设您缺少2012-02年度协议表中的条目，那么最好只包含一个包含日期的表.

Assuming you are missing an entry in your agreements table for 2012-02, it's always good to have a table containing simply dates.

CREATE TABLE dates(`date` date primary key);

DROP PROCEDURE IF EXISTS insertDates;
DELIMITER $$
CREATE PROCEDURE insertDates()
BEGIN
SET @start_date = '2010-01-01';
WHILE (@start_date <= '2010-12-31') DO
INSERT INTO dates VALUES (@start_date);
SET @start_date:=DATE_ADD(@start_date, INTERVAL 1 DAY);
END WHILE;
END $$
DELIMITER ;

CALL insertDates();

根据需要调整日期范围.

Adjust the date range according to your needs.

然后，您可以像下面这样编写查询.我简化了一点，因为我看不到需要变量或子查询.

Then you can write your query like the following. I simplified it a bit, since I saw no need for your variables or the subquery.

SELECT userId, DATE_FORMAT(dates.`date`, '%Y%M') AS timeUnit, 
  SUM(orderValue), 
  COUNT(orderValue),
  AVG(orderValue)
FROM 
dates LEFT JOIN
`agreements` ON dates.date = agreements.acceptDate
  WHERE userId = 4 
  AND acceptDate > '2000-00-00'
GROUP BY userId, timeUnit

更新:

SELECT userId, orgQuery.timeUnit, 
  @SUM := @SUM + orgQuery.orderValue AS sum, 
  @COUNT := @COUNT + 1 AS count, 
  @AVG := @SUM / @COUNT AS avg
    FROM (
    SELECT userid, orderValue,  
      DATE_FORMAT(dates.`date`, '%Y%M') AS timeUnit
FROM dates LEFT JOIN
`agreements` ON dates.date = agreements.acceptDate
    WHERE userId = 4 
    AND acceptDate > '2000-00-00' 
   GROUP BY timeUnit
)
AS orgQuery, 
  (SELECT @COUNT := 0, @SUM := 0,@AVG :=0) 
 AS extra GROUP BY timeUnit

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