MySQL 左外连接与 where 子句

Question

我正在尝试使用以下 MySQL 查询:

SELECT *
FROM top_lines t
LEFT OUTER JOIN last_24_topline AS l ON l.`member_no` = t.`member_no` 
    AND l.`mfg` = t.`line_no`
WHERE l.account_no = 32049 OR l.account_no IS NULL

然而，这没有返回任何行，因为 last_24_topline 中没有匹配的 account_no 行。据我了解和阅读，此查询仍应返回 top_lines 中的所有行，即使 last_24_topline 中没有匹配的行，因为我正在检查值或 null，但事实并非如此。 MySQL (5.7.2) 中是否有任何选项或设置会导致此行为？仅供引用，此查询按预期工作:

SELECT *
FROM top_lines t
LEFT OUTER JOIN last_24_topline l ON l.`member_no` = t.`member_no` 
    AND l.`mfg` = t.`line_no`
    AND l.`account_no` = 32049

但是我无法使用此构造，因为我使用的是 Entity Framework ，您只能将列传递给连接，而不能将值传递给连接

---

CREATE TABLE `last_24_topline` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `member_no` varchar(30) NOT NULL,
  `branch_no` int(11) DEFAULT NULL,
  `employee_no` varchar(25) DEFAULT NULL,
  `account_no` varchar(25) DEFAULT NULL,
  `salesperson_name` varchar(255) DEFAULT NULL,
  `customer_name` varchar(255) DEFAULT NULL,
  `mfg` varchar(5) DEFAULT NULL,
  `mfg_description` varchar(255) DEFAULT NULL,
  `last_three` decimal(10,2) DEFAULT '0.00',
  `last_twelve` decimal(10,2) DEFAULT '0.00',
  `ly_last_three` decimal(10,2) DEFAULT '0.00',
  `ly_last_twelve` decimal(10,2) DEFAULT '0.00',
  PRIMARY KEY (`id`),
  KEY `ix_branch_no` (`branch_no`),
  KEY `ix_employee_no` (`employee_no`),
  KEY `ix_member_line_account` (`member_no`,`mfg`,`account_no`),
  KEY `ix_member_line` (`member_no`,`mfg`),
  KEY `ix_account_no` (`account_no`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE `top_lines` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `member_no` varchar(30) NOT NULL,
  `line_no` varchar(5) NOT NULL,
  `line_description` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `ix_line_no` (`member_no`,`line_no`)
) ENGINE=InnoDB AUTO_INCREMENT=41 DEFAULT CHARSET=latin1

insert  into `top_lines`(`id`,`member_no`,`line_no`,`line_description`) values (1,'520','772','FED ROTOR/DRUM');
insert  into `top_lines`(`id`,`member_no`,`line_no`,`line_description`) values (2,'520','952','FED SST CERAMIC');
insert  into `top_lines`(`id`,`member_no`,`line_no`,`line_description`) values (3,'520','954','FED SST FRICTION');
insert  into `top_lines`(`id`,`member_no`,`line_no`,`line_description`) values (4,'520','162','EVS FRICTION');

INSERT INTO `last_24_topline` (`id`, `member_no`, `branch_no`, `employee_no`, `account_no`, `salesperson_name`, `customer_name`, `mfg`, `mfg_description`, `last_three`, `last_twelve`, `ly_last_three`, `ly_last_twelve`) VALUES('1','520','0','10856','463854','FORD, JAMES,','JIFFY LUBE','459','FEDERATED AIR FILTER','0.00','15.21','0.00','0.00');
INSERT INTO `last_24_topline` (`id`, `member_no`, `branch_no`, `employee_no`, `account_no`, `salesperson_name`, `customer_name`, `mfg`, `mfg_description`, `last_three`, `last_twelve`, `ly_last_three`, `ly_last_twelve`) VALUES('2','520','0','10856','463854','FORD, JAMES,','JIFFY LUBE','460','FILTERS','0.00','0.00','0.00','16.48');
INSERT INTO `last_24_topline` (`id`, `member_no`, `branch_no`, `employee_no`, `account_no`, `salesperson_name`, `customer_name`, `mfg`, `mfg_description`, `last_three`, `last_twelve`, `ly_last_three`, `ly_last_twelve`) VALUES('3','520','0','10856','463854','FORD, JAMES,','JIFFY LUBE','863','SMP T SERIES','0.00','0.00','0.00','50.67');

---

我希望，即使 last_24_topline 中没有匹配的数据，第一个查询也会生成一个结果集，其中包含 top_lines 中的所有行，而 last_24_topline 中的列的值为空。

预期结果:

---

因此，在另一个数据库中创建相同的模式并仅插入我在上面提供的示例数据，我得到了我期望的结果。我正在通过将完整行复制到第二个数据库来进一步测试，看看它是否仍然提供预期的结果。

更新将所有数据复制到新表中会导致问题再次出现。我正在尝试将重现该问题所需的最低限度减少。

Answer 1

也尝试检测空字符串，也许字段不是 NULL，而是空字符串。

SELECT *
FROM
    top_lines t
LEFT JOIN
    last_24_topline AS l ON l.member_no = t.member_no AND l.mfg = t.line_no
WHERE
    (l.account_no = '' OR l.account_no = '32049' OR l.account_no IS NULL)

如果您需要更多帮助，我将需要“table last_24_topline”的示例数据和加入后的预期输出。

作为第二次尝试，您可以使用这个:

SELECT *
FROM
    top_lines t
LEFT JOIN
    last_24_topline AS l ON l.member_no = t.member_no AND l.mfg = t.line_no
WHERE
    l.id IS NULL
OR
    (l.id IS NOT NULL AND l.account_no = '32049')