无法为设置了两个主键的 table 创建外键

Question

我正在尝试创建一个从一个 table 指向另一个的外键。这些是 tbl_inventory 和 tbl_player。玩家 table 设置了两个主键，player_score 和 playerID。当我尝试在清单 table 中创建外键以获取玩家 ID 时。它抛出以下错误：

这是我的 SQL 脚本：

drop database if exists example_db;
create database example_db;
use example_db;


/*Player  ===================================================================================*/
drop table if exists tbl_player; 
CREATE TABLE `tbl_player` (
    `player_score` INTEGER DEFAULT 0 NOT NULL,
    `playerID` INTEGER DEFAULT 0 NOT NULL,
    CONSTRAINT SYS_PK_10375 PRIMARY KEY (`player_score`,`playerID`)
);

/*Inventory ===================================================================================*/
drop table if exists tbl_inventory;
CREATE TABLE `tbl_inventory` (
    `inventoryID` INTEGER NOT NULL,
    `playerID` INTEGER DEFAULT 0 NOT NULL,
    CONSTRAINT SYS_PK_10520 PRIMARY KEY (`inventoryID`),
        FOREIGN KEY (playerID) REFERENCES tbl_player(playerID)
);

我做了一些故障排除，发现当我只定义一个主键时它可以工作，但我正在处理的项目需要两个。有人知道如何解决这个错误吗？

Answer 1

你有一个复合主键，所以你需要一个复合外键：

/*Inventory ===================================================================================*/
drop table if exists tbl_inventory;
CREATE TABLE `tbl_inventory` (
    `inventoryID` INTEGER NOT NULL,
    `playerID` INTEGER DEFAULT 0 NOT NULL,
    `player_score` INTEGER DEFAULT 0 NOT NULL,
    CONSTRAINT SYS_PK_10520 PRIMARY KEY (`inventoryID`),
    FOREIGN KEY (player_score,playerID) REFERENCES tbl_player(player_score,playerID)
);

您也可以尝试将一个主键和另一列作为唯一键：（仅当它适用于您的项目时，将 table 的单列作为主键，其他列作为唯一键）

/*Player  ===================================================================================*/
drop table if exists tbl_player; 
CREATE TABLE `tbl_player` (
    `player_score` INTEGER DEFAULT 0 NOT NULL,
    `playerID` INTEGER DEFAULT 0 NOT NULL,
    CONSTRAINT SYS_PK_10375 PRIMARY KEY (`playerID`),
    UNIQUE(`player_score`)
);

/*Inventory ===================================================================================*/
drop table if exists tbl_inventory;
CREATE TABLE `tbl_inventory` (
    `inventoryID` INTEGER NOT NULL,
    `playerID` INTEGER DEFAULT 0 NOT NULL,
    CONSTRAINT SYS_PK_10520 PRIMARY KEY (`inventoryID`),
    FOREIGN KEY (playerID) REFERENCES tbl_player(playerID)
);

干杯！！

无法为设置了两个主键的 table 创建外键

Cant create a foreign key for a table that has two primary keys set

mysql

sql

database

ddl