MySQL错误150 [英] MySQL Error 150

问题描述

我正在尝试创建一个脚本来规范化MySQL中的另一个表.以下是我所拥有的:

I'm trying to create a script to normalize another table in MySQL. Below is what I have:

USE  hw7;

SET foreign_key_checks = 0;
DROP TABLE IF EXISTS airport_codes;
DROP TABLE IF EXISTS airport_locations;
DROP TABLE IF EXISTS airport_codenames;
SET foreign_key_checks = 1;

CREATE TABLE airport_codes(
airport_code char(3) not null,
airline_code char(2) not null,
primary key (airport_code, airline_code)
);

INSERT INTO airport_codes SELECT DISTINCT airport_code, airline_code 
    FROM airport_airlines;

CREATE TABLE airport_locations(
airport_code char(3) not null,
city varchar(20) not null,
state char(2) not null,
primary key (airport_code),
constraint ap_code_fk
    foreign key (airport_code)
    references airport_codes(airport_code)
);

INSERT INTO airport_locations SELECT DISTINCT airport_code, city, state 
    FROM airport_airlines;

CREATE TABLE airport_codenames(
airline_code char(2) not null,
name varchar(20) not null,
primary key (airline_code),
constraint al_code_fk
    foreign key (airline_code)
    references airport_codes(airline_code)
);

INSERT INTO airport_codenames SELECT DISTINCT airline_code, name 
    FROM airport_airlines;

此代码会导致以下错误:

This code results in this error:

无法创建表hw7.airport_codenames errno:150

Can't create table hw7.airport_codenames errno:150

推荐答案

由于airport_codes每个airport_code和airline_code具有多个可能的行(作为组合键)，因此其他外键不能引用该行.将FK关系移到airport_codes，指向airport_locations和airport_codenames.

Since airport_codes has multiple possible rows per airport_code and airline_code (as a composite key), it cannot be referenced by other foreign keys. Move the FK relationships into airport_codes, pointing to airport_locations and airport_codenames.

USE  hw7;

SET foreign_key_checks = 0;
DROP TABLE IF EXISTS airport_codes;
DROP TABLE IF EXISTS airport_locations;
DROP TABLE IF EXISTS airport_codenames;
SET foreign_key_checks = 1;


CREATE TABLE airport_locations(
airport_code char(3) not null,
city varchar(20) not null,
state char(2) not null,
primary key (airport_code)
);

INSERT INTO airport_locations SELECT DISTINCT airport_code, city, state 
    FROM airport_airlines;

CREATE TABLE airport_codenames(
airline_code char(2) not null,
name varchar(20) not null,
primary key (airline_code)
);

INSERT INTO airport_codenames SELECT DISTINCT airline_code, name 
    FROM airport_airlines;


/* airport_codes moved after the other 2 tables, and FKs defined here */
CREATE TABLE airport_codes(
airport_code char(3) not null,
airline_code char(2) not null,
primary key (airport_code, airline_code),
/* FK relationships are defined here, rather than in the other tables,
   since the PKs for airport_code and airline_code are defined in the
   other tables.
*/
constraint ap_code_fk
    foreign key (airport_code)
    references airport_locations (airport_code),
constraint al_code_fk
    foreign key (airline_code)
    references airport_codenames (airline_code)
);

INSERT INTO airport_codes SELECT DISTINCT airport_code, airline_code 
    FROM airport_airlines;

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