MySQL LEFT JOIN与GROUP BY和WHERE IN(子查询)

Question

我有一个表,每个日期都有一些统计信息,我想用MySQL列出.某些日期没有统计数据,因此结果如下:
2013-03-01:3
2013-03-02:2
2013-03-03:0
2013-03-04:1

我发现填充0 -zero-的空隙可以通过一个单独的表来解决,该表包含所有可能的日期和LEFT JOIN.到现在为止还挺好.

统计数据(展示次数)位于"Campaigndata"表格中:

id - int(11)
date - date
campaignid - int(11)
impressions - int(11)

但我想只得到一些统计数据.更具体地说,我只想要'campaigndata'中的行,其中'campaignid'在表'campaignfilter'中,'campaigntype'设置为1(作为示例).

这是表'campaignfilter':

id - int(11)
campaigntype - int(11)
campaignid - int(11)

任何人都知道如何做到这一点？

PS:表'campaigndata'的结构几乎被锁定,因为它基于从外部系统自动导入.

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样本记录

CREATE TABLE demo_campaigndata (
  id int(11) NOT NULL AUTO_INCREMENT,
  date date NOT NULL,
  campaignid int(11) NOT NULL,
  impressions int(11) NOT NULL,
  PRIMARY KEY (id)
);
INSERT INTO demo_campaigndata (id, date, campaignid, impressions) VALUES
(1, '2013-03-03', 1, 100),
(2, '2013-03-03', 2, 100),
(3, '2013-03-03', 3, 100),
(4, '2013-03-04', 2, 100),
(5, '2013-03-05', 1, 100),
(6, '2013-03-05', 2, 100);


CREATE TABLE demo_campaignfilter (
  id int(11) NOT NULL AUTO_INCREMENT,
  campaigntype int(11) NOT NULL,
  campaignid int(11) NOT NULL,
  PRIMARY KEY (id)
);
INSERT INTO demo_campaignfilter (id, campaigntype, campaignid) VALUES
(1, 1, 1),
(2, 1, 3);


CREATE TABLE demo_calendar (
  date date NOT NULL,
  PRIMARY KEY (date)
);
INSERT INTO demo_calendar (date) VALUES
('2013-03-01'),
('2013-03-02'),
('2013-03-03'),
('2013-03-04'),
('2013-03-05');

期望的结果

2013-03-01: 0
2013-03-02: 0
2013-03-03: 200
2013-03-04: 0
2013-03-05: 100

Answer 1

SELECT  a.date, COUNT(b.campaignid) totalStat
FROM    campaigndata a
        LEFT JOIN campaignfilter b
            ON  a.campaignid = b.campaignid AND
                b.campaigntype = 1
GROUP   BY a.date

要进一步了解联接,请访问以下链接:

• SQL连接的可视化表示

更新1

SELECT  a.date, 
        COALESCE(b.totals,0) totals
FROM    demo_calendar a
        LEFT JOIN
        (
            SELECT  a.date, SUM(impressions) totals
            FROM    demo_campaigndata a
                    INNER JOIN demo_campaignfilter b
                        ON a.campaignid = b.campaignid
            WHERE   b.campaigntype = 1
            GROUP   BY a.date
        ) b ON a.date = b.date

• SQLFiddle演示