外鍵不「工作」？

Question

我正在爲一個學校項目創建一個報紙系統，這是該代碼的一部分。出於某種原因，我得到「錯誤代碼：1215無法添加外鍵約束」

-- MySQL Workbench Forward Engineering 

SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; 
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; 
SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES'; 

-- ----------------------------------------------------- 
-- Schema nyheterhiof 
-- ----------------------------------------------------- 

-- ----------------------------------------------------- 
-- Schema nyheterhiof 
-- ----------------------------------------------------- 
CREATE SCHEMA IF NOT EXISTS nyheterhiof DEFAULT CHARACTER SET utf8 ; 
USE nyheterhiof ; 

-- ----------------------------------------------------- 
-- Table nyheterhiof.newspapers 
-- ----------------------------------------------------- 
CREATE TABLE IF NOT EXISTS nyheterhiof.newspapers (
    newspaper_id INT(11) NOT NULL, 
    newspaper_name VARCHAR(45) NULL, 
    newspaper_city VARCHAR(45) NULL, 
    PRIMARY KEY (newspaper_id), 
    UNIQUE INDEX newspaper_id_UNIQUE (newspaper_id ASC)) 
ENGINE = InnoDB; 


-- ----------------------------------------------------- 
-- Table nyheterhiof.newspaper_Issues 
-- ----------------------------------------------------- 
CREATE TABLE IF NOT EXISTS nyheterhiof.newspaper_issues (
    newspaper_issiue_id INT(11) NOT NULL, 
    newspaper_id VARCHAR(45) NOT NULL, 
    publication_date DATE NOT NULL, 
    comment VARCHAR(200) NULL, 
    PRIMARY KEY (newspaper_issiue_id), 
    UNIQUE INDEX newspaper_issiue_id_UNIQUE (newspaper_issiue_id ASC), 
    INDEX fk_newspaper_Issues_newspapers1_idx (newspaper_id ASC), 
    CONSTRAINT fk_newspaper_Issues_newspapers1 
    FOREIGN KEY (newspaper_id) 
    REFERENCES newspapers (newspaper_id) 
    ON DELETE NO ACTION 
    ON UPDATE NO ACTION) 
ENGINE = InnoDB; 

我試圖移動FK的ALTER TABLE statment，我曾嘗試添加索引中「newspaper_issiues」到newspaper_id。

Answer 1

你指定

CREATE TABLE IF NOT EXISTS nyheterhiof.newspapers (
    newspaper_id INT(11) NOT NULL, 

和

CREATE TABLE IF NOT EXISTS nyheterhiof.newspaper_issues (
    ... 
    newspaper_id VARCHAR(45) NOT NULL, 

這就是問題所在。外鍵約束必須兩端的列匹配類型和寬度。

重新定義newspaper_issues.newspaper_id爲INT你會很好去。