Question

我想通过运行以下SQL来在MySQL中创建一个表，

CREATE TABLE IF NOT EXISTS `shrewd_db`.`alert_disable_register` (
  `id_alert_disable_register` MEDIUMINT NOT NULL AUTO_INCREMENT,
  `id_label` MEDIUMINT UNSIGNED NULL,
  `id_indicator` MEDIUMINT UNSIGNED NULL,
  `id_user` MEDIUMINT UNSIGNED NULL,
  `active` TINYINT(1) NULL DEFAULT 1,
  `id_alert_disable_rule` MEDIUMINT NULL,
  `id_escalation_plan` INT NULL,
  PRIMARY KEY (`id_alert_disable_register`),
  INDEX `id_escalation_plan_alert_rule_idx` (`id_alert_disable_rule` ASC),
  INDEX `id_label_idx` (`id_label` ASC),
  INDEX `id_indicator_idx` (`id_indicator` ASC),
  INDEX `id_user_idx` (`id_user` ASC),
  INDEX `id_escalation_plan_idx` (`id_escalation_plan` ASC),
  CONSTRAINT `id_label`
    FOREIGN KEY (`id_label`)
    REFERENCES `shrewd_db`.`escalation_plan` (`id_label`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_indicator`
    FOREIGN KEY (`id_indicator`)
    REFERENCES `shrewd_db`.`escalation_plan` (`id_indicator`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_user`
    FOREIGN KEY (`id_user`)
    REFERENCES `shrewd_db`.`escalation_plan_task_group_has_user` (`id_user`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_alert_disable_rule`
    FOREIGN KEY (`id_alert_disable_rule`)
    REFERENCES `shrewd_db`.`alert_disable_rule` (`id_alert_disable_rule`)
    ON DELETE SET NULL
    ON UPDATE SET NULL,
  CONSTRAINT `id_escalation_plan`
    FOREIGN KEY (`id_escalation_plan`)
    REFERENCES `shrewd_db`.`escalation_plan` (`id_escalation_plan`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

但我收到了以下错误，

错误1005（HY000）：无法创建表格 'shrewd_db.alert_disable_register'（错误号：150）

任何人都可以帮我解决这个问题，:)

请在下面找到下面其他所需表格的脚本，

CREATE TABLE `escalation_plan` (
  `id_escalation_plan` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_indicator` mediumint(8) unsigned NOT NULL,
  `id_label` mediumint(8) unsigned NOT NULL,
  `pressure_waiting_hrs` int(11) NOT NULL DEFAULT '6',
  PRIMARY KEY (`id_escalation_plan`),
  KEY `fk_escalation_plan_escalation_plan1_idx` (`id_indicator`),
  KEY `fk_escalation_plan_label1_idx` (`id_label`),
  CONSTRAINT `fk_escalation_plan_escalation_plan1` FOREIGN KEY (`id_indicator`) REFERENCES `indicator` (`id_indicator`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_escalation_plan_label1` FOREIGN KEY (`id_label`) REFERENCES `label` (`id_label`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=152 DEFAULT CHARSET=utf8;


CREATE TABLE `escalation_plan_task_group_has_user` (
  `id_escalation_plan_task_has_user` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_user` mediumint(8) unsigned NOT NULL,
  `id_escalation_plan_task_group` int(11) NOT NULL,
  `text_alert` tinyint(1) NOT NULL DEFAULT '1',
  `email_alert` tinyint(1) NOT NULL DEFAULT '1',
  PRIMARY KEY (`id_escalation_plan_task_has_user`),
  KEY `fk_escalation_plan_task_has_user_user1_idx` (`id_user`),
  KEY `fk_escalation_plan_task_group_has_user_escalation_plan_task_idx` (`id_escalation_plan_task_group`),
  CONSTRAINT `fk_escalation_plan_task_group_has_user_escalation_plan_task_g1` FOREIGN KEY (`id_escalation_plan_task_group`) REFERENCES `escalation_plan_task_group` (`id_escalation_plan_task_group`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_escalation_plan_task_has_user_user1` FOREIGN KEY (`id_user`) REFERENCES `user` (`id_user`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=3605 DEFAULT CHARSET=utf8;


CREATE TABLE `alert_disable_rule` (
  `id_alert_disable_rule` mediumint(9) NOT NULL AUTO_INCREMENT,
  `disable_in_weekend` tinyint(1) DEFAULT '0',
  `start_date` datetime DEFAULT NULL,
  `end_date` datetime DEFAULT NULL,
  `start_time` decimal(10,0) DEFAULT NULL,
  `end_time` decimal(10,0) DEFAULT NULL,
  PRIMARY KEY (`id_alert_disable_rule`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

为了使外键约束成功，必须满足以下条件：

数据类型¹且符号必须匹配
引用的表必须在相关列上具有最左侧的²索引，以便快速进行约束验证。
整理可以起到一个作用。请参阅我的answer。

在你的情况下，索引很好，但正如Solarflare所提到的，只有你的数据类型在这里很重要并且不匹配：

`alert_disable_register`.`id_escalation_plan`-- signed int
`escalation_plan`.`id_escalation_plan` -- unsigned int

请注意，显示宽度（括号中的数字）和可空性无关紧要。

从Mysql手册页Using FOREIGN KEY Constraints：

外键和引用键中的对应列必须   有类似的数据类型。整数类型的大小和符号必须是   相同。字符串类型的长度不必相同。对于   非二进制（字符）字符串列，字符集和排序规则   必须是一样的。

MySQL要求外键和引用键上的索引   外键检查可以很快，不需要表扫描。在里面   引用表时，必须有一个索引所在的外键   列以相同的顺序列为第一列。

外键和引用键中的对应列必须   有类似的数据类型。整数类型的大小和符号必须是   相同。字符串类型的长度不必相同。对于   非二进制（字符）字符串列，字符集和排序规则   必须是一样的。

另请注意，满足FK关系的引用的表键不需要是主键，甚至不是唯一键。排序中第一个（也称为最左侧 ²）以满足。

同样，索引不是你的问题，但通常是针对其他人。

对于那些需要在创建表后添加外键约束的人，请使用ALTER TABLE语句。

以下测试运行正常。您需要自己决定如何处理自己的更改。你错过了一些提供的表格，这些表格需要在前两个表格中删除一些FK约束。

create database xyztest123;
use xyztest123;


CREATE TABLE `escalation_plan` (
  `id_escalation_plan` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_indicator` mediumint(8) unsigned NOT NULL,
  `id_label` mediumint(8) unsigned NOT NULL,
  `pressure_waiting_hrs` int(11) NOT NULL DEFAULT '6',
  PRIMARY KEY (`id_escalation_plan`),
  KEY `fk_escalation_plan_escalation_plan1_idx` (`id_indicator`),
  KEY `fk_escalation_plan_label1_idx` (`id_label`)
  -- CONSTRAINT `fk_escalation_plan_escalation_plan1` FOREIGN KEY (`id_indicator`) REFERENCES `indicator` (`id_indicator`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  -- CONSTRAINT `fk_escalation_plan_label1` FOREIGN KEY (`id_label`) REFERENCES `label` (`id_label`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=152 DEFAULT CHARSET=utf8;


CREATE TABLE `escalation_plan_task_group_has_user` (
  `id_escalation_plan_task_has_user` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_user` mediumint(8) unsigned NOT NULL,
  `id_escalation_plan_task_group` int(11) NOT NULL,
  `text_alert` tinyint(1) NOT NULL DEFAULT '1',
  `email_alert` tinyint(1) NOT NULL DEFAULT '1',
  PRIMARY KEY (`id_escalation_plan_task_has_user`),
  KEY `fk_escalation_plan_task_has_user_user1_idx` (`id_user`),
  KEY `fk_escalation_plan_task_group_has_user_escalation_plan_task_idx` (`id_escalation_plan_task_group`)
  -- CONSTRAINT `fk_escalation_plan_task_group_has_user_escalation_plan_task_g1` FOREIGN KEY (`id_escalation_plan_task_group`) REFERENCES `escalation_plan_task_group` (`id_escalation_plan_task_group`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  -- CONSTRAINT `fk_escalation_plan_task_has_user_user1` FOREIGN KEY (`id_user`) REFERENCES `user` (`id_user`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=3605 DEFAULT CHARSET=utf8;


CREATE TABLE `alert_disable_rule` (
  `id_alert_disable_rule` mediumint(9) NOT NULL AUTO_INCREMENT,
  `disable_in_weekend` tinyint(1) DEFAULT '0',
  `start_date` datetime DEFAULT NULL,
  `end_date` datetime DEFAULT NULL,
  `start_time` decimal(10,0) DEFAULT NULL,
  `end_time` decimal(10,0) DEFAULT NULL,
  PRIMARY KEY (`id_alert_disable_rule`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;



CREATE TABLE IF NOT EXISTS  `alert_disable_register` (
  `id_alert_disable_register` MEDIUMINT NOT NULL AUTO_INCREMENT,
  `id_label` MEDIUMINT UNSIGNED NULL,
  `id_indicator` MEDIUMINT UNSIGNED NULL,
  `id_user` MEDIUMINT UNSIGNED NULL,
  `active` TINYINT(1) NULL DEFAULT 1,
  `id_alert_disable_rule` MEDIUMINT NULL,
  `id_escalation_plan` INT unsigned NULL,
  PRIMARY KEY (`id_alert_disable_register`),
  INDEX `id_escalation_plan_alert_rule_idx` (`id_alert_disable_rule` ASC),
  INDEX `id_label_idx` (`id_label` ASC),
  INDEX `id_indicator_idx` (`id_indicator` ASC),
  INDEX `id_user_idx` (`id_user` ASC),
  INDEX `id_escalation_plan_idx` (`id_escalation_plan` ASC),
  CONSTRAINT `id_label`
    FOREIGN KEY (`id_label`) -- MEDIUMINT UNSIGNED 
    REFERENCES  `escalation_plan` (`id_label`) -- mediumint(8) unsigned , -- Index OK?: Yes
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_indicator`
    FOREIGN KEY (`id_indicator`) -- MEDIUMINT UNSIGNED 
    REFERENCES  `escalation_plan` (`id_indicator`) -- mediumint(8) unsigned, -- Index OK?: Yes
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_user`
    FOREIGN KEY (`id_user`) -- MEDIUMINT UNSIGNED  
    REFERENCES  `escalation_plan_task_group_has_user` (`id_user`) -- mediumint(8) unsigned, -- Index OK?: Yes
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `id_alert_disable_rule`
    FOREIGN KEY (`id_alert_disable_rule`) -- MEDIUMINT 
    REFERENCES  `alert_disable_rule` (`id_alert_disable_rule`) -- mediumint(9),  -- Index OK?: Yes
    ON DELETE SET NULL
    ON UPDATE SET NULL,
  CONSTRAINT `id_escalation_plan`
    FOREIGN KEY (`id_escalation_plan`) -- INT 
    REFERENCES  `escalation_plan` (`id_escalation_plan`) -- int(10) unsigned, Index OK?: Yes
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

drop database xyztest123;

¹类似且允许的列差异，字符串数据

drop table if exists a2; -- must do in reverse order
drop table if exists a1;
create table a1
(   id int auto_increment primary key,
    thing varchar(100) not null,
    key `keyname001` (thing)
)ENGINE = InnoDB;
create table a2
(   id int auto_increment primary key,
    myThing char(40) not null, -- similar and allowable datatype
    foreign key `fk_002` (myThing) references a1(thing)
)ENGINE = InnoDB;
insert a2(myThing) values ('a'); -- error 1452, FK violation
insert a1(thing) values ('a'); -- ok
insert a2(myThing) values ('a'); -- ok, not FK violation

-- now a redo below to show it slightly different

drop table if exists a2; -- must do in reverse order
drop table if exists a1;
create table a1
(   id int auto_increment primary key,
    thing varchar(100) not null,
    key `keyname001` (thing)
)ENGINE = InnoDB;
create table a2
(   id int auto_increment primary key,
    myThing varchar(30) not null, -- similar and allowable datatype
    key(myThing),
    foreign key `fk_002` (myThing) references a1(thing)
)ENGINE = InnoDB;
insert a2(myThing) values ('a'); -- error 1452, FK violation
insert a1(thing) values ('a'); -- ok
insert a2(myThing) values ('a'); -- ok, not FK violation

²最左/最常索引排序

单个列上的索引（a.k.a. a key ）是最左边的，因为它不是复合索引。

父列表中的多列索引（也称为复合索引）（引用的）表是最令人满意的，如果其列的顺序在与子表关键字相同的顺序，依赖于它的外键（FK）关系。即使该父组合键中的列数大于子组合键的计数。见下面的例子。

假设子（引用）表具有按(col1,col4)排序的复合键FK要求，那么

由(col1,col2,col3,col4)排序的父组合键不符合最左边的要求。
按(col1,col4,col3, ...)排序的父组合键确实满足最左边的要求。

这里的内容是，如果这样的父键不是最令人满意的，那么子表CREATE TABLE的语句将因FK关系而失败。创建表的尝试将失败，错误代码为1215。

同样地，存在的孩子的ALTER TABLE将失败，试图在事后添加FK关系。

ERROR 1005（HY000）：无法创建表'shrewd_db.alert_disable_register'（错误号：150）

1 个答案:

¹类似且允许的列差异，字符串数据

²最左/最常索引排序

ERROR 1005（HY000）：无法创建表'shrewd_db.alert_disable_register'（错误号：150）

1 个答案:

1 类似且允许的列差异，字符串数据

2 最左/最常索引排序

¹类似且允许的列差异，字符串数据

²最左/最常索引排序