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));
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)