字段定义constraint 约束名约否类型(字段名)-->unique,primary key,check 字段定义constraint 约否名foreingn key (字段名)references 表名(字段名)--->foreign 三、建表时约束定义 1.定义各种不同的约束 --创建一个用于作外键的表tb_dept SQL> CREATE TABLE tb_dept 2 ( 3 deptno NUMBER(4) PRIMARY KEY...
(2,'Robert','Luna',22,'USA');-- insert record into table with foreign key constraint in customer_id column-- Insertion SuccessINSERTINTOOrdersVALUES(1,'Keyboard',400,2), (2,'Mouse',300,2), (3,'Monitor',12000,1); Run Code Here, the query is successfully sql-executed as the rows ...
SELECT*FROMchild_tableWHEREparent_id=1;-- 根据查询结果决定是否删除关联数据行DELETEFROMparent_tableWHEREid=1; 1. 2. 3. 4. 5. 序列图 下面是一个序列图,展示了Delete操作中涉及到的相关表之间的关系和操作流程: DatabaseServerClientDatabaseServerClient发起Delete请求执行Delete操作检查外键约束返回结果返回删...
TheINSERTstatement conflictedwiththeFOREIGNKEYconstraint"fk_class". The conflict occurredindatabase "SampleDb",table"dbo.Classes",column'class_id'. 在本例中,学生老王的class_id为4,但是在Classes表中没有class_id为4的班级,由于(FOREIGN KEY)外键约束,SQL Server拒绝了插入并发出错误。 外键引用的行为 外键...
PRIMARYKEY(OrderID), FOREIGNKEY(PersonID)REFERENCESPersons(PersonID) ); SQL Server / Oracle / MS Access: CREATETABLEOrders ( OrderID intNOTNULLPRIMARYKEY, OrderNumber intNOTNULL, PersonID intFOREIGNKEYREFERENCESPersons(PersonID) ); To allow naming of aFOREIGN KEYconstraint, and for defining aFOR...
DELETEFROMemployeeterritoriesWHEREemployeeID =3Code language:SQL (Structured Query Language)(sql) Typically, database management systems allow you to create aforeign key constraintso that if you delete a row in a table, the corresponding rows in the related table are also removed automatically. ...
ALTER TABLE [表名] ADD CONSTRAINT 默认值名 DEFAULT \'51WINDOWS.NET\' FOR [字段名] 删除默认值 ALTER TABLE [表名] DROP CONSTRAINT 默认值名 删除Sql Server 中的日志,减小数据库文件大小 dump transaction 数据库名 with no_log backup log 数据库名 with no_log ...
by a FOREIGN KEY constraint. 1. 2. SQL Server不允许删除外部约束引用的表。 要删除此表,必须先删除引用外键约束或引用表。 在这种情况下,必须先删除 supplier 表或 supplier 表中的外键约束,然后再删除 supplier_groups 表。 DROP TABLE procurement.supplier_groups; ...
DELETE * FROM table_name SQL Server中每一条select、insert、update、delete语句都是隐形事务的一部分,显性事务用BEGIN TRANSACTION明确指定事务。 链接:https://www.nowcoder.com/questionTerminal/5d309f0bea9a4c6b946d9852ade64f6c 来源:牛客网 并发一致性问题,指的是在并发环境下,因为事务的隔离性很难保证,所...
Requires ALTER permission on the table. Use SQL Server Management Studio To delete a foreign key constraint In Object Explorer, expand the table with the constraint and then expand Keys. Right-click the constraint and then select Delete. In the Delete Object dialog box, select OK. Use Transact...