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如何在MySQL DB中识别外键？

2024-04-27 20:09:05 397

让我们首先创建一个表-

mysql> create table DemoTable1 (Id int NOT NULL PRIMARY KEY,EmployeeName varchar(100));

以下是创建具有外键约束的第二个表的查询-

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)
   );

以下是在MySQLDB中标识外键的查询-

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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如何在MySQL DB中识别外键？

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