Question

我正在尝试选择不在另一个表中的行。在这里，我已将 LEFT JOIN 与 IS NULL 结合使用，但没有得到预期的结果。它仅对一个表有效，而对另一个表无效。

主要是我无法管理四个表之间的关系。 fee-包括费用类别）和fee_tm-包括要支付费用的月份列表，cls_fee-每个类别的费用标准）和invoice-包含有关已付费用的信息费用）。

结果，我试图显示未付款的学生名单，或不在invoice表中的那些学生记录。

Mysql

SELECT
    fee_tm.id AS ftm_d,
    fee.id AS f_id,
    fee_tm.en_ttl AS f_tm,
    fee.en_ttl AS fee,
    cls_fee.fee AS f_mnt
FROM
    fee
LEFT JOIN
    fee_tm ON fee_tm.year = fee.year
LEFT JOIN
    cls_fee ON cls_fee.fee_id = fee.id
LEFT JOIN
    student ON student.cls = cls_fee.c_id AND student.sec = cls_fee.s_id
LEFT JOIN
    invoice ON invoice.stu_id = student.id AND invoice.fee_id = fee.id AND invoice.ftm_id = fee_tm.id
WHERE
    student.id =1 AND invoice.ftm_id is NULL AND invoice.fee_id is NULL

当前结果

ftm_d   |   f_id    |   f_tm    |   fee     |   f_mnt
=====================================================
2       |   1       |   Feb     |   Annual  |   1000
2       |   2       |   Feb     |   Monthly |   560

预期结果

ftm_d   |   f_id    |   f_tm    |   fee     |   f_mnt
=====================================================
2       |   2       |   Feb     |   Monthly |   560

我的结果仅检查f_tm列，因此在我的当前结果月份Jan被过滤，但它还必须检查fee列和Annual行必须被过滤。

因此，我们可以知道尚未支付学费的学生。如果在invoice表中找到该记录，则应在结果中过滤此费用类别。

数据库结构

学生

id  |   en_ttl  |   cls |   sec |   year
========================================
1   |   John    |   1   |   1   |   1

cls

id  |   en_ttl  |   year
========================
1   |   One     |   1

秒

id  |   en_ttl  |   year
========================
1   |   A       |   1

费用

id  |   en_ttl  |   year
========================
1   |   Annual  |   1
2   |   Monthly |   1
3   |   Library |   1

fee_tm

id  |   en_ttl  |   year
========================
1   |   Jan     |   1
2   |   Feb     |   1

cls_fee

id  |   c_id    |   s_id    |   fee_id  |   fee
===============================================
1   |   1       |   1       |   1       |   1000
2   |   1       |   1       |   2       |   560

发票

id  |   stu_id  |   fee_id  |   ftm_id
======================================
1   |   1       |   1       |   1

表的DDL语句

CREATE TABLE `student` (
 `id` int(4) NOT NULL AUTO_INCREMENT,
 `en_ttl` varchar(100) NOT NULL,
 `cls` int(2) NOT NULL,
 `sec` int(2) NOT NULL,
 `year` int(1) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

CREATE TABLE `cls` (
 `id` int(2) NOT NULL AUTO_INCREMENT,
 `en_ttl` varchar(50) NOT NULL,
 `year` int(2) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

CREATE TABLE `sec` (
 `id` int(2) NOT NULL AUTO_INCREMENT,
 `en_ttl` varchar(50) NOT NULL,
 `year` int(2) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

CREATE TABLE `fee` (
 `id` int(2) NOT NULL AUTO_INCREMENT,
 `en_ttl` varchar(50) NOT NULL,
 `year` int(2) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

CREATE TABLE `fee_tm` (
 `id` int(2) NOT NULL AUTO_INCREMENT,
 `en_ttl` varchar(50) NOT NULL,
 `year` int(2) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

CREATE TABLE `cls_fee` (
 `id` int(2) NOT NULL AUTO_INCREMENT,
 `c_id` int(2) NOT NULL,
 `s_id` int(2) NOT NULL,
 `fee_id` int(2) NOT NULL,
 `fee` int(6) NOT NULL,
 PRIMARY KEY (`id`),
 UNIQUE KEY `fee` (`c_id`,`s_id`,`fee_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;

CREATE TABLE `invoice` (
 `id` int(4) NOT NULL AUTO_INCREMENT,
 `stu_id` int(4) NOT NULL,
 `fee_id` int(11) NOT NULL,
 `ftm_id` int(11) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1;

Answer 1

在cluase中使用studentid = 1

    SELECT
    fee_tm.id AS ftm_d,
    fee.id AS f_id,
    fee_tm.en_ttl AS f_tm,
    fee.en_ttl AS fee,
    cls_fee.fee AS f_mnt
    FROM
    fee
inner JOIN
    fee_tm ON fee_tm.year = fee.year and fee.id=fee_tm.id inner join cls_fee on cls_fee.fee_id = fee.id
    LEFT JOIN
    student ON student.cls = cls_fee.c_id AND student.sec = cls_fee.s_id
    left join invoice  ON invoice.stu_id = student.id AND invoice.fee_id = fee.id AND invoice.ftm_id = fee_tm.id and student.id=1
    where invoice.fee_id is null

LEFT JOIN / IS NULL无法按预期工作-仅选择不在另一个表中的行

1 个答案: