使用左连接求和和

Question

我需要查询报告的帮助。我在此方案的底部有一个发票表，需要一种方法来获得总计费金额，同时在此数据库方案中的较高点有条件地过滤。我需要加入其他表，导致SUM函数返回不需要的结果。

这是我正在使用的一般方案的图表。

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) ;

以下是我正在使用的查询。

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中的总计费用是375.此查询返回1125，这是错误的！如果我按照i.iid进行分组，由于某种原因我得到三次回报 - 看似是由于租约和隔间之间的一对多关系。我已尝试过其他分组方式并离开加入，但没有什么能让我获得准确的数字。

Answer 1

问题是你的连接都是向后的（并且无论如何都应该保持连接）。我喜欢从最简单的查询开始并从那里开始构建。

1. 您需要根据林进行过滤，林是hcm_leases表的一部分：

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

1. 现在您想获得林中所有租约的发票1.发票通过合同与租约相关联：

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;

1. 您希望能够根据segment表中的hcm_compartments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;

1. 但你真正想要的是收费金额的总和（按财政年度过滤）：

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，如果不希望按segment进行过滤，则必须将JOIN忽略为hcm_compartments，因为MySQL不知道联接创建的两个不同的行，bid ='1'，segment ='1'和bid ='1'，segment ='2'不是唯一的。

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;

使用子查询可以实现相同的答案，同时保留对hcm_compartments的连接，但由于您的结果集不包含该表中的任何字段，因此看起来最简单的方法就是完全省略它