计算列不能作为PRIMARY KEY、UNIQUE、FOREIGN KEY或DEFAULT约束定义的一部分; 计算列不能用INSERT和UPDATE语句插入资料。 注意:① 在建表语句中,不允许对计算列设置空值属性(NULL或NOT NULL); ② 在建表语句中,列与列的定义用逗号分隔,当将PRIMARY KEY设置在最后时, 如果最后一列是常规列,则它后面的...
|{ ENABLE|DISABLE }TRIGGER{ALL|<触发器名>[, n]} |DROP--【删除列或约束】 {[CONSTRAINT]<约束名>--删除某个约束 |COLUMN<column_name>}[, n]--删除某列 |{CHECK|NOCHECK}CONSTRAINT{ALL|<约束名>[, n]} |{ENABLE|DISABLE}TRIGGER{ALL|<trigger_name>[, n]} |SWITCH[PARTITION ]...
FeatureFOREIGN KEYApplies to:Azure SQL Database and SQL Server starting SQL Server 2016 (13.x) For memory-optimized tables, FOREIGN KEY constraints are only supported for foreign keys referencing primary keys of other memory-optimized tables. Remove the constraint from the table definition if the ...
◆ CONSTRAINT constraint_name:建立约束。CONSTRAINT为可选关键字,表示PRIMARY KEY, NOT NULL, UNIQUE, FOREIGN KEY或CHECK约束定义的开始。constraint_name是约束的名称。约束名称必须在表所属的架构中唯一。 ◆ DEFAULT constant_expression:如果在插入过程中未显式提供值,则指定为列提供的值。constant_expression是列...
CONSTRAINT ISOLATION SUBSTRING CONSTRAINTS JOIN SUM CONTINUE KEY SYSTEM_USER CONVERT LANGUAGE TABLE CORRESPONDING LAST TEMPORARY COUNT LEADING THEN CREATE LEFT TIME CROSS LEVEL TIMESTAMP CURRENT LIKE TIMEZONE_HOUR CURRENT_DATE LOCAL TIMEZONE_MINUTE CURRENT_TIME LOWER 收件人 CURRENT_TIMESTAM...
{ALL|<constraint_name>[,...n]}|{ENABLE|DISABLE}TRIGGER{ALL|<trigger_name>[,...n]}|SWITCH[PARTITION ]TO[schema_name.]target_table[PARTITION<target partition number expression>]} 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. ...
CREATE [ CONSTRAINT ] TRIGGER name { BEFORE | AFTER | INSTEAD OF } { event [ OR ... ]} ON table_name [ FROM referenced_table_name ] [ NOT DEFERRABLE | [ DEFERRABLE ] [ INITIALLY IMMEDIATE | INITIALLY DEFERRED ] ] [ REFERENCING { { OLD | NEW } TABLE [...
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使用T-SQL进行数据定义 数据库技术与应用（电子商务系列）使用T-SQL进行数据定义 一、数据库定义 •（一）T-SQL语句创建数据库的语法格式 •CREATEDATABASE数据库名 //设置数据库的名称 •[ON //定义数据库的数据文件 •[PRIMARY]//设置主文件组 •<数据文件描述符>[,…n]//设置数据文件的属性 •...
USE AdventureWorks2022; GO UPDATE HumanResources.EmployeePayHistory SET PayFrequency = 4 WHERE BusinessEntityID = 1; IF @@ERROR = 547 BEGIN PRINT N'A check constraint violation occurred.'; END GO B. 利用 @@ERROR 有條件地結束程序 下列範例會在預存程序中的 DELETE 陳述式之後,使用 IF...ELSE...