mysql - 左连接和条件 where 求和

Question

我需要有关报告查询的帮助。我在该方案的底部有一个发票表，需要一种方法来获取总计费金额，同时在此数据库方案中的较高点进行条件过滤。我需要加入其他表，这会导致 SUM 函数返回不需要的结果。

这是我正在使用的总体方案的图表。

这是数据库设置。

CREATE TABLE `hcm_compartments` (
`cid` int(10) NOT NULL AUTO_INCREMENT,
`leaseid` int(10) NOT NULL,
`segment` int(10) NOT NULL DEFAULT '0',
PRIMARY KEY (`cid`),
KEY `leaseid` (`leaseid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `hcm_contracts` (
`cid` int(10) NOT NULL AUTO_INCREMENT,
`leaseid` int(10) NOT NULL,
`groupid` int(11) DEFAULT NULL,
`license` varchar(100) NOT NULL,
`dateadded` int(10) NOT NULL DEFAULT '0',
`BeginDate` int(10) DEFAULT NULL,
PRIMARY KEY (`cid`),
KEY `leaseid` (`leaseid`),
KEY `groupid` (`groupid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `hcm_forest` (
`ForestID` int(10) NOT NULL AUTO_INCREMENT,
`ForestName` varchar(50) NOT NULL,
`ForestLabel` varchar(5) NOT NULL,
PRIMARY KEY (`ForestID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `hcm_invoices` (
`iid` int(10) NOT NULL AUTO_INCREMENT,
`contractid` int(10) NOT NULL DEFAULT '0',
`dateadded` int(10) NOT NULL DEFAULT '0',
`fiscalyear` int(4) NOT NULL DEFAULT '0',
`totalbilled` decimal(10,2) NOT NULL DEFAULT '0.00',
`totalpaid` decimal(10,2) NOT NULL DEFAULT '0.00',
`balance` decimal(10,2) NOT NULL DEFAULT '0.00',
PRIMARY KEY (`iid`),
KEY `contractid` (`contractid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `hcm_leases` (
`bid` int(11) NOT NULL AUTO_INCREMENT,
`serial` int(10) NOT NULL DEFAULT '0',
`forest` int(10) NOT NULL DEFAULT '0',
`dateadded` int(10) NOT NULL DEFAULT '0',
`acres` decimal(10,2) NOT NULL DEFAULT '0.00',
PRIMARY KEY (`bid`),
KEY `forest` (`forest`),
KEY `serial` (`serial`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;


SET @timenow = UNIX_TIMESTAMP(NOW());

INSERT INTO hcm_forest (ForestID, ForestName, ForestLabel) VALUES (1, 'North', 'N'), (2, 'South', 'S'), (3, 'East', 'E'), (4, 'West', 'W') ;
INSERT INTO hcm_leases (bid, serial, forest, dateadded, acres)
VALUES
(1, 1000, 1, @timenow, 100),
(2, 1001, 2, @timenow, 125),
(3, 1002, 3, @timenow, 250) ;

INSERT INTO hcm_compartments (leaseid, segment)
VALUES
(1, 1),(1, 2),(1, 3),
(2, 1),(2, 2),(2, 3), (2, 4),
(3, 1),(3, 2),(3, 3) ;

INSERT INTO hcm_contracts (leaseid, groupid, license, dateadded, BeginDate)
VALUES
(1, 1, 'N-1000', @timenow, @timenow),
(2, 2, 'N-1000', @timenow, @timenow),
(3, 3, 'N-1000', @timenow, @timenow) ;

INSERT INTO hcm_invoices (contractid, dateadded, fiscalyear, totalbilled, totalpaid, balance)
VALUES
(1, @timenow, 2016, 125.00, 125.00, 0.00),
(1, @timenow, 2016, 150.00, 0.00, 150.00),
(1, @timenow, 2016, 100.00, 75.00, 25.00),

(2, @timenow, 2016, 1000.00, 125.00, 875.00),
(2, @timenow, 2016, 550.00, 550.00, 0.00),
(2, @timenow, 2016, 100.00, 0.00, 100.00),
(2, @timenow, 2016, 5000.00, 4500.00, 500.00),

(3, @timenow, 2016, 100.00, 100.00, 0.00),
(3, @timenow, 2016, 250.00, 50.00, 200.00) ;

这是我正在处理的查询。

SET @fy = 2016 ;

SELECT SUM(i.totalbilled) totalbilled, l.forest
FROM hcm_leases l,
    hcm_compartments cm,
    hcm_contracts c,
    hcm_invoices i
WHERE i.contractid = c.cid
    AND c.leaseid = l.bid
    AND l.bid = cm.leaseid
    /*
    * The reason why I join into the hcm_compartments table is
    * because the user may wish to exclude all but a single
    * desired segment column from the hcm_compartments table.
    */
    #AND cm.segment = 1
    AND l.forest = 1
    AND i.fiscalyear = @fy ;

林 1 中的总计费为 375。此查询返回 1125，这是错误的!如果我按 i.iid 进行分组，由于某种原因，我会得到三个返回值 - 似乎是由于租约和隔间之间的一对多关系。我尝试过其他分组和离开加入的方法，但没有任何方法可以为我提供准确的数字。

Answer 1

问题是你的连接都是向后的(无论如何应该是左连接)。我喜欢从最简单的查询开始，然后从那里开始构建。

1. 您需要根据森林进行过滤，森林是 hcm_leases 表的一部分:

SELECT `l`.`forest` FROM `hcm_leases` `l` WHERE `l`.`forest` = 1;

现在您想要获取森林 1 中所有租赁的发票。发票通过契约(Contract)与租赁相关联:

SELECT `i`.`totalbilled`, `l`.`forest` FROM `hcm_leases` `l`
    LEFT JOIN `hcm_contracts` `c` ON `l`.`bid` = `c`.`leaseid`
    LEFT JOIN `hcm_invoices` `i` ON `i`.`contractid` = `c`.`cid`
WHERE `l`.`forest` = 1;

您希望能够根据 hcm_compartments 表中的segment 进行过滤:

SELECT `i`.`totalbilled`, `l`.`forest` FROM `hcm_leases` `l`
    LEFT JOIN `hcm_contracts` `c` ON `l`.`bid` = `c`.`leaseid`
    LEFT JOIN `hcm_invoices` `i` ON `i`.`contractid` = `c`.`cid`
    LEFT JOIN `hcm_compartments` `cm` ON `cm`.`leaseid` = `l`.`bid`
WHERE `l`.`forest` = 1 AND `cm`.`segment` = 1;

但您真正想要的是账单金额的总和(并按会计年度过滤):

SELECT SUM(`i`.`totalbilled`) `totalbilled`, `l`.`forest` FROM `hcm_leases` `l`
    LEFT JOIN `hcm_contracts` `c` ON `l`.`bid` = `c`.`leaseid`
    LEFT JOIN `hcm_invoices` `i` ON `i`.`contractid` = `c`.`cid`
    LEFT JOIN `hcm_compartments` `cm` ON `cm`.`leaseid` = `l`.`bid`
WHERE `l`.`forest` = 1 
    AND `cm`.`segment` = 1
    AND `i`.`fiscalyear` = @fy;

结果:

+-------------+--------+
| totalbilled | forest |
+-------------+--------+
|      375.00 |      1 |
+-------------+--------+

现在，如果您不想按分割进行过滤，则必须省略JOIN到hcm_compartments 因为 MySQL 不知道连接创建的两个不同行，bid='1',segment='1' 和 bid='1',segment='2' 不唯一。

SELECT SUM(`i`.`totalbilled`) `totalbilled`, `l`.`forest` FROM `hcm_leases` `l`
    LEFT JOIN `hcm_contracts` `c` ON `l`.`bid` = `c`.`leaseid`
    LEFT JOIN `hcm_invoices` `i` ON `i`.`contractid` = `c`.`cid`
 WHERE `l`.`forest` = 1 
    AND `i`.`fiscalyear` = @fy;

通过子查询可能可以实现相同的答案，同时保留与 hcm_compartments 的连接，但由于您的结果集不包含该表中的任何字段，因此这似乎是最简单的方法完全省略它。