MySQL 如何在MySQL DB中识别外键

让我们首先创建一个表 –

mysql> create table DemoTable1 (Id int NOT NULL PRIMARY KEY,EmployeeName varchar(100));
Query OK, 0 rows affected (0.50 sec)

下面是使用外键约束创建第二个表的查询 –

mysql> create table DemoTable2
    (
        Id int NOT NULL,
        StreetName varchar(100),
        CityName varchar(100),
        CountryName varchar(100),
        PinCode int,
        EmployeeId int,
        PRIMARY KEY(Id),
        FOREIGN KEY (Id) REFERENCES DemoTable1(Id)
    );
Query OK, 0 rows affected (0.46 sec)

以下是识别MySQL DB中外键的查询 –

mysql> show create table DemoTable2\G

这将产生以下输出 –

*************************** 1. row ***************************
Table: DemoTable2
Create Table: CREATE TABLE `demotable2` (
    `Id` int(11) NOT NULL,
    `StreetName` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL,
    `CityName` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL,
    `CountryName` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL,
    `PinCode` int(11) DEFAULT NULL,
    `EmployeeId` int(11) DEFAULT NULL,
    PRIMARY KEY (`Id`),
    CONSTRAINT `demotable2_ibfk_1` FOREIGN KEY (`Id`) REFERENCES `demotable1`
(`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
1 row in set (0.00 sec)

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