Mysql sum distinct 基于包含多个 LEFT JOIN 的其他列

Question

我有 5 个表我想一起 LEFT JOIN。表格是： 访客、报价、合同 1、合同 2 和合同 3。

查询：

SELECT 
        count(DISTINCT visitors.ID) as visitors, 
        sum(
        CASE
        WHEN offers.ACTIVE = 1 THEN 1
        ELSE 0
        END) as offers, 
        count(contracts1.ID) as contracts1, sum(contracts1.PRICE) as sum_contracts1, 
        count(contracts2.ID) contracts2, 
        sum(
        CASE
        WHEN contracts2.PAYMENT = 'YEARLY' THEN contracts2.PRICE
        WHEN contracts2.PAYMENT = 'TWICE' THEN contracts2.PRICE*2
        ELSE contracts2.PRICE*4
        END) as sum_contracts2,
        count(contracts3.ID) as contracts3, sum(contracts3.PRICE) as sum_contracts3
        FROM visitors 
        LEFT JOIN offersON offers.VISITOR_ID = visitors.ID AND (offers.IP > 100 OR offers.IP < 0)
        LEFT JOIN contracts1 ON 
        (offers.ID = contracts1.ID_OFFER)
        LEFT JOIN contracts2 ON 
        (offers.ID = contracts2.ID_OFFER)
        LEFT JOIN contracts3 ON 
        (offers.ID = contracts3.ID_OFFER)
        WHERE  visitors.TIME >= '2017-01-01 00:00:00' AND visitors.TIME <= '2017-05-25 23:59:59'

这里的问题是，contracts1、contracts2 和contracts3 没有共同的列来连接在一起。因此，我得到了所有这些组合的所有组合，而不是contracts1 的 20 行、contracts2 的 30 行和contracts3 的 50 行。因为他们是根据访客和提供表格加入的。查询末尾的简单 GROUP BY 通常可以解决问题，但是如果我在 END 中对这些表之一（或所有表）使用 GROUP BY，它将创建 MULTIPLE ROWS 而不是我想要的 1。而且它还会删除我按 ID 计算访问者并按 ID 提供的部分的所有其他结果......我可以在 SELECT 的 count() 部分使用 DISTINCT，但不能使用 sum() 因为合同的 PRICE即使 ID 不同，也可能相同（例如，您知道 2 块巧克力是 2 行，ID 不同，但价格相同，每块 10 美元）。

所以我的问题是：

有没有什么方法可以只对具有 DISTINCT ID 的合同 1、合同 2 和合同 3 的价格进行求和，但可以避免重复项相加？是否可以不创建 VIEW？

我还在 LEFT JOIN 中尝试了 GROUP BY，但是当我将所有 3 个合同表一起 LEFT JOINED 时，即使我在最终得到重复项之前对它们进行了分组。

预期结果示例：

在我上面所说的那个时间范围内，我期望： 80 名参观者有 35 份报​​价和 5 份总金额为 1000 欧元的合同 1、12 份总金额为 686 欧元的合同 2 和 3 份总金额为 12 欧元的合同 3。它是 ONE ROW，有 8 列数据。

我得到的不是预期的结果： 80 位访客，35 份报​​价，180 份合同1（金额也很差），180 份合同2（金额也很差），180 份合同3（金额也很差）。

Answer 1

使用 CTE (Supported by MariaDB 10.2.1) 我会写这样的东西：

WITH v AS (
    SELECT ID as VISITOR_ID
    FROM visitors 
    WHERE visitors.TIME >= '2017-01-01 00:00:00'
      AND visitors.TIME <= '2017-05-25 23:59:59'
), o AS (
    SELECT offers.ID as ID_OFFER
    FROM v
    JOIN offers USING(VISITOR_ID)
    WHERE offers.ACTIVE = 1
      AND (offers.IP > 100 OR offers.IP < 0)
), c1 AS (
    SELECT count(*) as contracts1, sum(contracts1.PRICE) as sum_contracts1
    FROM o JOIN contracts1 USING(ID_OFFER)
), c2 AS (
    SELECT
        count(*) contracts2, 
        sum(CASE contracts2.PAYMENT
            WHEN 'YEARLY' THEN contracts2.PRICE
            WHEN 'TWICE'  THEN contracts2.PRICE*2
            ELSE contracts2.PRICE*4
        END) as sum_contracts2
    FROM o JOIN contracts2 USING(ID_OFFER)
), c3 AS (
    SELECT count(*) as contracts3, sum(contracts3.PRICE) as sum_contracts3
    FROM o JOIN contracts3 USING(ID_OFFER)
)
    SELECT c1.*, c2.*, c3.*,
        (SELECT count(*) FROM v) as visitors,
        (SELECT count(*) FROM o) as offers,
    FROM c1, c2, c3;

如果没有 CTE，您可以重写它以使用临时表：

CREATE TEMPORARY TABLE v AS
    SELECT ID as VISITOR_ID
    FROM visitors 
    WHERE visitors.TIME >= '2017-01-01 00:00:00'
      AND visitors.TIME <= '2017-05-25 23:59:59';

CREATE TEMPORARY TABLE o AS
    SELECT offers.ID as ID_OFFER
    FROM v
    JOIN offers USING(VISITOR_ID)
    WHERE offers.ACTIVE = 1
      AND (offers.IP > 100 OR offers.IP < 0);

CREATE TEMPORARY TABLE c1 AS
    SELECT count(*) as contracts1, sum(contracts1.PRICE) as sum_contracts1
    FROM o JOIN contracts1 USING(ID_OFFER);

CREATE TEMPORARY TABLE c2 AS
    SELECT
        count(*) contracts2, 
        sum(CASE contracts2.PAYMENT
            WHEN 'YEARLY' THEN contracts2.PRICE
            WHEN 'TWICE'  THEN contracts2.PRICE*2
            ELSE contracts2.PRICE*4
        END) as sum_contracts2
    FROM o JOIN contracts2 USING(ID_OFFER);

CREATE TEMPORARY TABLE c3 AS
    SELECT count(*) as contracts3, sum(contracts3.PRICE) as sum_contracts3
    FROM o JOIN contracts3 USING(ID_OFFER);

SELECT c1.*, c2.*, c3.*,
    (SELECT count(*) FROM v) as visitors,
    (SELECT count(*) FROM o) as offers,
FROM c1, c2, c3;

Answer 2

只是一个概念证明，我不考虑时间和活动限制以及付款类型，但它不能是类似的东西吗？

SELECT
   VISITOR_ID,
   SUM(CASE WHEN TYPE="contract1" THEN 1 else 0 END) as c1_count,
   SUM(CASE WHEN TYPE="contract1" THEN PRICE else 0 END) as c1_total_price,
   SUM(CASE WHEN TYPE="contract2" THEN 1 else 0 END) as c2_count,
   SUM(CASE WHEN TYPE="contract2" THEN PRICE else 0 END) as c2_total_price,
   SUM(CASE WHEN TYPE="contract3" THEN 1 else 0 END) as c3_count,
   SUM(CASE WHEN TYPE="contract3" THEN PRICE else 0 END) as c3_total_price 
FROM (
    (SELECT "contract1" as TYPE, ID, PRICE, ID_OFFER, PAYMENT FROM contracts1) 
    UNION
    (SELECT "contract2" as TYPE, ID, PRICE, ID_OFFER, PAYMENT FROM contracts2)
    UNION
    (SELECT "contract3" as TYPE, ID, PRICE, ID_OFFER, PAYMENT FROM contracts3)
 ) as all_contracts 
 JOIN offers on offers.id = all_contracts.ID_OFFER
 JOIN visitors on visitors.ID = offers.VISITOR_ID
 GROUP BY visitors.ID

这个想法是，首先你将不同的合约合并到一个结果中，你将它们的类型存储在一个名为“TYPE”的列中（这就是 UNION 查询的目的），一旦你有一个如此好的表，其中每个合约都是准确的一次，您可以非常简单地获得所需的结果。我刚刚概述了您如何获得每种合同类型的总和和计数。当然，最终的查询会稍微复杂一些，但核心思想应该是一样的。

但是，尽管您声明您不想使用（临时）视图，但我还是鼓励您尝试一下 - 我觉得将这些“all_contracts”与优惠和访问者一起放入临时视图会改善性能，如果这是您关心的问题，而不会使查询太难看，主要是在您只想查看一位访问者的统计信息或进一步过滤它们（按时间、活动等）的情况下，因为不必要的行不会t 被物化。但这只是一个印象，因为我没有在更大的数据集上尝试过查询 - 你可以玩一下。