在 MySQL 表中创建引用日期的唯一键?
mysqlmysqli database
要在 MySQL 表中创建引用日期的唯一键，您可以使用以下语法 −
CREATE TABLE yourTableName ( yourIdColumnName dataType, yourDateColumnName dataType, . . . N UNIQUE KEY(yourIdColumnName, yourDateColumnName ) );
为了理解上述语法，让我们创建一个表。创建表的查询如下 −
mysql> create table keyReferringToDateDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Client_Id int, -> ClientProjectDeadline date, -> ClientName varchar(100), -> ClientAge int, -> ClientCountryName varchar(20) , -> UNIQUE KEY(Client_Id,ClientProjectDeadline) -> ); Query OK, 0 rows affected (0.63 sec)
让我们使用 SHOW CREATE 命令检查表的所有详细信息。查询如下 −
mysql> show create table keyReferringToDateDemo;
这是输出 −
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------+ | Table | Create Table | +------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | keyReferringToDateDemo | CREATE TABLE `keyreferringtodatedemo` (`Id` int(11) NOT NULL AUTO_INCREMENT,`Client_Id` int(11) DEFAULT NULL,`ClientProjectDeadline` date DEFAULT NULL,`ClientName` varchar(100) DEFAULT NULL,`ClientAge` int(11) DEFAULT NULL,`ClientCountryName` varchar(20) DEFAULT NULL,PRIMARY KEY (`Id`),UNIQUE KEY `Client_Id` (`Client_Id`,`ClientProjectDeadline`) ) ENGINE =InnoDB DEFAULT CHARSET =utf8 | +------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
