为什么这些查询在MySQL 5.5和5.6中产生不同的结果？

有人能解释一下为什么这两个查询（一个在中使用

，另一个使用
存在
）在MySQL 5.6中返回不同的结果，而在MySQL 5.5中却没有

通过使用
EXPLAIN
，我可以看到每个项目的不同执行计划，但我需要帮助了解发生了什么，以及为什么
逻辑中的
会在5.6而不是5.5中被破坏

Fiddle举例说明问题：

成员可以有两个地址：家庭地址和公司地址。所需的结果是提供一个区域X，并获得该区域中具有邮寄地址的所有成员的列表。邮寄地址是公司地址（如果存在），否则是家庭地址。城市可以属于一个或多个地区

简化的数据库结构和数据：

CREATE TABLE `city` (
  `c_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `c_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`c_id`)
);

INSERT INTO `city`
VALUES
  ('1', 'Hillsdale'),
  ('2', 'Smallville'),
  ('3', 'Oakside'),
  ('4', 'Lakeview');

CREATE TABLE `city_region` (
  `cr_city` int(11) unsigned NOT NULL,
  `cr_region` int(11) NOT NULL,
  PRIMARY KEY (`cr_city`,`cr_region`)
);

INSERT INTO `city_region`
VALUES
  ('1', '3'),
  ('2', '1'),
  ('3', '1'),
  ('3', '2'),
  ('4', '1'),
  ('4', '3');

CREATE TABLE `firm_address` (
  `fa_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `fa_member` int(11) NOT NULL,
  `fa_city` int(11) NOT NULL,
  PRIMARY KEY (`fa_id`)
);

INSERT INTO `firm_address`
VALUES
  ('1', '1', '3'),
  ('2', '2', '2'),
  ('3', '3', '1'),
  ('4', '6', '2'),
  ('5', '7', '1');

CREATE TABLE `home_address` (
  `ha_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `ha_member` int(11) NOT NULL,
  `ha_city` int(11) NOT NULL,
  PRIMARY KEY (`ha_id`)
);

INSERT INTO `home_address`
VALUES
  ('1', '1', '2'),
  ('2', '2', '3'),
  ('3', '3', '1'),
  ('4', '4', '1'),
  ('5', '5', '2'),
  ('6', '6', '2');

CREATE TABLE `member` (
  `m_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `m_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`m_id`)
);

INSERT INTO `member`
VALUES
  ('1', 'John'),
  ('2', 'Bob'),
  ('3', 'Dave'),
  ('4', 'Jane'),
  ('5', 'Mary'),
  ('6', 'Karen'),
  ('7', 'Christie');

CREATE TABLE `region` (
  `r_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `r_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`r_id`)
);

INSERT INTO `region`
VALUES
  ('1', 'Central'),
  ('2', 'Lake District'),
  ('3', 'Westside');

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE 1 IN (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
)

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE EXISTS (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
    AND r_id = 1
)

查询1（错误，缺少成员）：

CREATE TABLE `city` (
  `c_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `c_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`c_id`)
);

INSERT INTO `city`
VALUES
  ('1', 'Hillsdale'),
  ('2', 'Smallville'),
  ('3', 'Oakside'),
  ('4', 'Lakeview');

CREATE TABLE `city_region` (
  `cr_city` int(11) unsigned NOT NULL,
  `cr_region` int(11) NOT NULL,
  PRIMARY KEY (`cr_city`,`cr_region`)
);

INSERT INTO `city_region`
VALUES
  ('1', '3'),
  ('2', '1'),
  ('3', '1'),
  ('3', '2'),
  ('4', '1'),
  ('4', '3');

CREATE TABLE `firm_address` (
  `fa_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `fa_member` int(11) NOT NULL,
  `fa_city` int(11) NOT NULL,
  PRIMARY KEY (`fa_id`)
);

INSERT INTO `firm_address`
VALUES
  ('1', '1', '3'),
  ('2', '2', '2'),
  ('3', '3', '1'),
  ('4', '6', '2'),
  ('5', '7', '1');

CREATE TABLE `home_address` (
  `ha_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `ha_member` int(11) NOT NULL,
  `ha_city` int(11) NOT NULL,
  PRIMARY KEY (`ha_id`)
);

INSERT INTO `home_address`
VALUES
  ('1', '1', '2'),
  ('2', '2', '3'),
  ('3', '3', '1'),
  ('4', '4', '1'),
  ('5', '5', '2'),
  ('6', '6', '2');

CREATE TABLE `member` (
  `m_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `m_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`m_id`)
);

INSERT INTO `member`
VALUES
  ('1', 'John'),
  ('2', 'Bob'),
  ('3', 'Dave'),
  ('4', 'Jane'),
  ('5', 'Mary'),
  ('6', 'Karen'),
  ('7', 'Christie');

CREATE TABLE `region` (
  `r_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `r_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`r_id`)
);

INSERT INTO `region`
VALUES
  ('1', 'Central'),
  ('2', 'Lake District'),
  ('3', 'Westside');

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE 1 IN (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
)

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE EXISTS (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
    AND r_id = 1
)

查询2（返回正确的结果）：

CREATE TABLE `city` (
  `c_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `c_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`c_id`)
);

INSERT INTO `city`
VALUES
  ('1', 'Hillsdale'),
  ('2', 'Smallville'),
  ('3', 'Oakside'),
  ('4', 'Lakeview');

CREATE TABLE `city_region` (
  `cr_city` int(11) unsigned NOT NULL,
  `cr_region` int(11) NOT NULL,
  PRIMARY KEY (`cr_city`,`cr_region`)
);

INSERT INTO `city_region`
VALUES
  ('1', '3'),
  ('2', '1'),
  ('3', '1'),
  ('3', '2'),
  ('4', '1'),
  ('4', '3');

CREATE TABLE `firm_address` (
  `fa_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `fa_member` int(11) NOT NULL,
  `fa_city` int(11) NOT NULL,
  PRIMARY KEY (`fa_id`)
);

INSERT INTO `firm_address`
VALUES
  ('1', '1', '3'),
  ('2', '2', '2'),
  ('3', '3', '1'),
  ('4', '6', '2'),
  ('5', '7', '1');

CREATE TABLE `home_address` (
  `ha_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `ha_member` int(11) NOT NULL,
  `ha_city` int(11) NOT NULL,
  PRIMARY KEY (`ha_id`)
);

INSERT INTO `home_address`
VALUES
  ('1', '1', '2'),
  ('2', '2', '3'),
  ('3', '3', '1'),
  ('4', '4', '1'),
  ('5', '5', '2'),
  ('6', '6', '2');

CREATE TABLE `member` (
  `m_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `m_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`m_id`)
);

INSERT INTO `member`
VALUES
  ('1', 'John'),
  ('2', 'Bob'),
  ('3', 'Dave'),
  ('4', 'Jane'),
  ('5', 'Mary'),
  ('6', 'Karen'),
  ('7', 'Christie');

CREATE TABLE `region` (
  `r_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `r_name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`r_id`)
);

INSERT INTO `region`
VALUES
  ('1', 'Central'),
  ('2', 'Lake District'),
  ('3', 'Westside');

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE 1 IN (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
)

SELECT * FROM member

LEFT OUTER JOIN home_address ON m_id = ha_member
LEFT OUTER JOIN city home_city ON ha_city = home_city.c_id
LEFT OUTER JOIN firm_address ON m_id = fa_member
LEFT OUTER JOIN city firm_city ON fa_city = firm_city.c_id

WHERE EXISTS (
    SELECT r_id
    FROM region
    INNER JOIN city_region ON r_id = cr_region
    WHERE cr_city = IF(fa_city IS NULL, ha_city, fa_city)
    AND r_id = 1
)

如果您能帮助理解这种不一致性，我们将不胜感激

谢谢。
我今天花了一些时间研究这个问题，它似乎是MySQL 5.6中的一个bug。（我还测试了MySQL 5.6.15，得到了相同的结果。）

MySQL 5.6在执行此查询时使用了一些新的优化，但它们似乎并不是造成差异的原因，因为这无助于设置，例如：

set session optimizer_switch="block_nested_loop=off";

使用
IFNULL（fa_city，ha_city）
而不是
IF（fa_city为NULL，hau city，fau city）
确实会产生正确的结果，因此错误似乎在WHERE子句的子查询中处理
IF（）
是
r_id
是否为NULL？请编辑您的查询，使其具有表别名。无法判断列的来源。这两个查询给出了相同的结果，请查看此演示：结果在v5.5中相同，但在5.6中不同，更新的问题澄清了这一点。感谢您指出这一点，我认为它更多地与
IF（）
函数有关，而不是与
中的
运算符有关。我将
WHERE cr_city=IF（fa_city为NULL，ha_city，fa_city）
更改为
WHERE cr_city=IFNULL（fa_city，ha_city）
它开始在两个版本中工作。您还应该检查它是否在最新版本的MYSQL 5.6（目前为5.6.15）中工作，在SqlFIDLE上有5.6.6）Jeremy。谢谢你看这个。我将向mysql提交一张罚单，并在等待期结束时奖励赏金。您是否在中创建了错误罚单？如果是，我可以看到它的URL吗？