mysql - 组合两个查询而不省略行

Question

我有两个表，我需要这两个表中的记录。

查询 1

SELECT SUM(rec_issued) AS issed,
       regen_id,
       YEAR(issue_date) AS iYear,
       MONTH(issue_date) AS iMonth
FROM `view_rec_issued`
WHERE `regen_id` = 2
GROUP BY YEAR(issue_date) DESC, MONTH(issue_date) DESC
ORDER BY issue_date ASC

给出这个结果：

| issed | regen_id | iYear | iMonth |
-------------------------------------
|   424 |        2 |  2011 |      3 |
|  4340 |        2 |  2011 |      4 |
|  4235 |        2 |  2011 |      5 |
| 10570 |        2 |  2012 |      2 |
|  4761 |        2 |  2012 |      3 |
|  5000 |        2 |  2012 |      4 |
|  3700 |        2 |  2012 |      5 |
|  3414 |        2 |  2012 |      6 |
|  3700 |        2 |  2012 |      7 |
|  2992 |        2 |  2012 |      8 |
|   995 |        2 |  2012 |     10 |

查询 2

SELECT SUM(total_redem) AS redemed,
       regen_id,
       YEAR(redemption_date) AS rYear,
       MONTH(redemption_date) AS rMonth
FROM `recredem_month_wise`
WHERE `regen_id` = 2
GROUP BY YEAR(redemption_date) DESC, MONTH(redemption_date) DESC
order by redemption_date ASC

给出这个结果：

| redemed | regen_id | rYear | rMonth |
---------------------------------------
|     424 |        2 |  2011 |      3 |
|     260 |        2 |  2011 |      4 |
|    6523 |        2 |  2011 |      5 |
|    1070 |        2 |  2011 |      6 |
|     200 |        2 |  2011 |     10 |
|     500 |        2 |  2011 |     11 |
|    9750 |        2 |  2012 |      2 |
|    5000 |        2 |  2012 |      3 |
|    5500 |        2 |  2012 |      4 |
|    3803 |        2 |  2012 |      5 |
|    3700 |        2 |  2012 |      7 |
|    3000 |        2 |  2012 |      8 |

期望的结果

但我想要这样：

|  issed | regen_id |  iYear | iMonth | redemed | regen_id |  rYear | rMonth |
-------------------------------------------------------------------------------
|    424 |        2 |   2011 |      3 |     424 |        2 |   2011 |      3 |
|   4340 |        2 |   2011 |      4 |     260 |        2 |   2011 |      4 |
|   4235 |        2 |   2011 |      5 |    6523 |        2 |   2011 |      5 |
|   NULL |     NULL |   NULL |   NULL |    1070 |        2 |   2011 |      6 |
|   NULL |     NULL |   NULL |   NULL |     200 |        2 |   2011 |     10 |
|   NULL |     NULL |   NULL |   NULL |     500 |        2 |   2011 |     11 |
|  10570 |        2 |   2012 |      2 |    9750 |        2 |   2012 |      2 |
|   4761 |        2 |   2012 |      3 |    5000 |        2 |   2012 |      3 |
|   5000 |        2 |   2012 |      4 |    5500 |        2 |   2012 |      4 |
|   3700 |        2 |   2012 |      5 |    3803 |        2 |   2012 |      5 |
|   3414 |        2 |   2012 |      6 |    NULL |     NULL |   NULL |   NULL |
|   3700 |        2 |   2012 |      7 |    3700 |        2 |   2012 |      7 |
|   2992 |        2 |   2012 |      8 |    3000 |        2 |   2012 |      8 |
|    995 |        2 |   2012 |     10 |    NULL |     NULL |   NULL |   NULL |

在这些表中regen_id是唯一的，我需要数据YEAR和MONTH. 如果一个表在特定月份和年份中没有任何记录，那么它应该检索零或NULL。

但在每一个创纪录的年份和月份都应该像这样 -

 iYear = rYear and iMonth = rMonth

所以我们可以合并两个字段 - 不需要显示年份和月份两次

iYear and rYear = year
iMonth and rMonth = month

更新

我试过这个查询，几乎解决了这个问题，但记录不是以“YEAR DESC，MONTH DESC”的形式排序的。

SELECT DISTINCT A.issed, A.regen_id, A.iYear AS yrs, A.iMonth AS mnt, B.redemed, B.regen_id, B.rYear AS yrs, B.rMonth AS mnt
FROM(SELECT SUM(rec_issued) AS issed, regen_id, YEAR(issue_date) AS iYear, MONTH(issue_date) AS iMonth  
FROM `view_rec_issued` 
WHERE `regen_id` = 2 
GROUP BY YEAR(issue_date) DESC, MONTH(issue_date) DESC 
ORDER BY issue_date ASC) AS A 
LEFT JOIN 
(SELECT SUM(total_redem) AS redemed, regen_id, YEAR(redemption_date) AS rYear, MONTH(redemption_date) AS rMonth
FROM `recredem_month_wise` 
WHERE `regen_id` = 2 
GROUP BY YEAR(redemption_date) DESC, MONTH(redemption_date) DESC 
ORDER BY redemption_date ASC) AS B ON A.iYear = B.rYear AND A.iMonth = B.rMonth

UNION

SELECT DISTINCT A.issed, A.regen_id, A.iYear AS yrs, A.iMonth AS mnt, B.redemed, B.regen_id, B.rYear AS yrs, B.rMonth AS mnt
FROM(SELECT SUM(rec_issued) AS issed, regen_id, YEAR(issue_date) AS iYear, MONTH(issue_date) AS iMonth  
FROM `view_rec_issued` 
WHERE `regen_id` = 2 
GROUP BY YEAR(issue_date) DESC, MONTH(issue_date) DESC 
ORDER BY issue_date ASC) AS A 
RIGHT JOIN 
(SELECT SUM(total_redem) AS redemed, regen_id, YEAR(redemption_date) AS rYear, MONTH(redemption_date) AS rMonth 
FROM `recredem_month_wise` 
WHERE `regen_id` = 2 
GROUP BY YEAR(redemption_date) DESC, MONTH(redemption_date) DESC 
ORDER BY redemption_date ASC) AS B ON A.iYear = B.rYear AND A.iMonth = B.rMonth

score 1 · Accepted Answer

您所描述的称为 a ：您想要两个表中的所有行，如果未找到匹配项，则FULL OUTER JOIN填充另一个表。NULL不幸的是，MySQL 不提供完整的外部连接，因此您必须模拟它们。

另请参阅MySQL 中的完全外部联接。

模拟完全外连接的规范方式

编写此方法的一种方法如下，它NULL为丢失的匹配项生成。

(SELECT I.iYear AS `year`, I.iMonth AS `month`, I.issed, R.redeemed
 FROM (
  SELECT SUM(rec_issued) AS issed,
         regen_id,
         YEAR(issue_date) AS iYear,
         MONTH(issue_date) AS iMonth
  FROM `view_rec_issued`
  WHERE `regen_id` = 2
  GROUP BY YEAR(issue_date), MONTH(issue_date)
 ) I
 LEFT JOIN (
  SELECT SUM(total_redem) AS redemed,
         regen_id,
         YEAR(redemption_date) AS rYear,
         MONTH(redemption_date) AS rMonth
  FROM `recredem_month_wise`
  WHERE `regen_id` = 2
  GROUP BY YEAR(redemption_date), MONTH(redemption_date)
 ) R
 ON (I.iYear = R.rYear AND I.iMonth = R.rMonth)
)
UNION DISTINCT
(SELECT R.iYear AS `year`, R.iMonth AS `month`, I.issed, R.redeemed
 FROM (
  SELECT SUM(total_redem) AS redemed,
         regen_id,
         YEAR(redemption_date) AS rYear,
         MONTH(redemption_date) AS rMonth
  FROM `recredem_month_wise`
  WHERE `regen_id` = 2
  GROUP BY YEAR(redemption_date), MONTH(redemption_date)
 ) R
 LEFT JOIN (
  SELECT SUM(rec_issued) AS issed,
         regen_id,
         YEAR(issue_date) AS iYear,
         MONTH(issue_date) AS iMonth
  FROM `view_rec_issued`
  WHERE `regen_id` = 2
  GROUP BY YEAR(issue_date), MONTH(issue_date)
 ) I
 ON (I.iYear = R.rYear AND I.iMonth = R.rMonth)
)
ORDER BY `year` ASC, `month` ASC

您可以通过为其包含的子查询编写视图来缩短它，但如果您希望能够更改regen_id，那么这仍然是相当庞大的代码。

与零联合

您可以通过完全避免外部连接来使事情变得更容易，而是使用不同的联合，将零填充到如下所示的行中：

SELECT YEAR(`date`) AS `year`, MONTH(`date`) AS `month`,
       SUM(rec_issued) AS issued, SUM(total_redem) AS redeemed
FROM (
    SELECT issue_date AS `date`, rec_issued, 0 AS total_redem
    FROM view_rec_issued WHERE regen_id = 2
  UNION ALL
    SELECT redemption_date AS `date`, 0 AS rec_issued, total_redem
    FROM redemption_month_wise WHERE regen_id = 2
  ) AS U
GROUP BY EXTRACT(YEAR_MONTH FROM `date`) ASC

左加入所有子查询查找月份

下表进行外连接模拟只是为了查找出现在任一表中的日期。然后它会进行左连接来计算总和。因此，它将返回零而不是NULL缺失值。

SELECT LEFT(DI.ym, 4) + 0 AS `year`, RIGHT(DI.ym, 2) + 0 AS `month`,
       DI.issed, SUM(R.total_redem) AS redeemed
FROM
 (SELECT D.ym, SUM(I.rec_issued) AS issed
  FROM
   (SELECT DISTINCT EXTRACT(YEAR_MONTH FROM issue_date) as ym
    FROM view_rec_issued
    WHERE regen_id = 2
   UNION DISTINCT
    SELECT DISTINCT EXTRACT(YEAR_MONTH FROM redemtion_date) AS ym
    FROM recredem_month_wise
    WHERE regen_id = 2
   ) AS D
  LEFT JOIN view_rec_issued AS I
         ON I.regen_id = 2
        AND EXTRACT(YEAR_MONTH FROM I.issue_date) = D.ym
 ) AS DI
LEFT JOIN recredem_month_wise AS R
       ON R.regen_id = 2
      AND EXTRACT(YEAR_MONTH FROM R.redemtion_date) = DI.ym
GROUP BY DI.ym ASC

这将不得不比上面的查询多看一次每个表，所以它可能会更慢。如果您担心性能，只需尝试两者并对其进行基准测试。就代码长度而言，这里的这个查询要紧凑得多，我相信也更具可读性。

请注意，上述查询在这篇文章的过去修订版中有所不同。该版本省略了子查询DI。结果更容易阅读，但不幸的是错误的：如果一个月内有两个问题和三个赎回，那么连接将把这个月的六行合并，因此每个问题计算三次，每个赎回计算两次。

到目前为止，所有查询都未经测试。如果您的问题在http://sqlfiddle.com/上附带了一些示例数据，那么在将它们发布到此处之前，我会在那里尝试我的查询。

score 0 · Accepted Answer

按以下顺序试一试：

SELECT * FROM 
(SELECT DISTINCT A.issed, A.regen_id, A.iYear, A.iMonth, B.redemed, B.regen_id, B.rYear, B.rMonth
FROM (SELECT SUM(rec_issued) AS issed, regen_id, YEAR(issue_date) AS iYear, MONTH(issue_date) AS iMonth  
FROM `view_rec_issued` 
WHERE `regen_id` = 2 
GROUP BY YEAR(issue_date) DESC, MONTH(issue_date) DESC 
ORDER BY issue_date ASC) AS A 
LEFT JOIN 
(SELECT SUM(total_redem) AS redemed, regen_id, YEAR(redemption_date) AS rYear, MONTH(redemption_date) AS rMonth 
FROM `recredem_month_wise` 
WHERE `regen_id` = 2 
GROUP BY YEAR(redemption_date) DESC, MONTH(redemption_date) DESC 
ORDER BY redemption_date ASC) AS B ON A.iYear = B.rYear AND A.iMonth = B.rMonth
UNION 
SELECT DISTINCT A.issed, A.regen_id, A.iYear, A.iMonth, B.redemed, B.regen_id, B.rYear, B.rMonth
FROM (SELECT SUM(rec_issued) AS issed, regen_id, YEAR(issue_date) AS iYear, MONTH(issue_date) AS iMonth  
FROM `view_rec_issued` 
WHERE `regen_id` = 2 
GROUP BY YEAR(issue_date) DESC, MONTH(issue_date) DESC 
ORDER BY issue_date ASC) AS A 
RIGHT JOIN 
(SELECT SUM(total_redem) AS redemed, regen_id, YEAR(redemption_date) AS rYear, MONTH(redemption_date) AS rMonth 
FROM `recredem_month_wise` 
WHERE `regen_id` = 2 
GROUP BY YEAR(redemption_date) DESC, MONTH(redemption_date) DESC 
ORDER BY redemption_date ASC) AS B ON A.iYear = B.rYear AND A.iMonth = B.rMonth) AS C
ORDER BY iYear DESC, iMonth DESC