DROP a FOREIGN KEY Constraint To drop aFOREIGN KEYconstraint, use the following SQL: MySQL: ALTERTABLEOrders DROPFOREIGNKEYFK_PersonOrder; SQL Server / Oracle / MS Access: ALTERTABLEOrders DROPCONSTRAINTFK_Perso
'] DROP CONSTRAINT [' + name + ']' FROM sys.foreign_keys WHERE referenced_object_id = object_id('Student')智能推荐SQL 数据库主键 ,外键 主键 数据库主键是指表中一个列或列的组合,其值能唯一地标识表中的每一行。这样的一列或多列称为表的主键,通过它可强制表的实体完整性。当创建或更改表时...
(select object_id from sys.tables where name = 'TableName') ) 列出主外键关系 select t.name as TableWithForeignKey, fk.constraint_column_id as FK_PartNo , c.name as ForeignKeyColumn from sys.foreign_key_columns as fk inner join sys.tables as t on fk.parent_object_id = t.object_id ...
Here, the query is successfully sql-executed as the rows we are trying to insert in theOrderstable have valid values in thecustomer_idcolumn, which has aFOREIGN KEYconstraint in theCustomerstable. Insertion Failure in Foreign Key An insertion failure occurs when a value is entered into a table...
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, 4 deptname VARCHAR2(20), ...
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, 4 deptname VARCHAR2(20), ...
[CONSTRAINT <约束名>][FOREIGN KEY][<列名>]REFERENCES<被参照表名>(<主键列名>) 例如 --删除外键 alter table AdItem drop constraint AdOrder_AdItem_FK1 www.2cto.com --增加外键 alter table AdItem add constraint AdOrder_AdItem_FK1 foreign key (AI_nOrderNo) references AdOrder(AO_nOrderNo) ...
DROPPRIMARYKEY; DROP a FOREIGN KEY Constraint To drop a FOREIGN KEY constraint, use the following SQL: SQL Server / Oracle / MS Access: ALTERTABLEOrders DROPCONSTRAINTFK_PersonOrder; MySQL: ALTERTABLEOrders DROPFOREIGNKEYFK_PersonOrder;
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; ...
Multiple tables can be dropped in the sameDROP TABLEstatement. If both the referencing table in aFOREIGN KEYconstraint and the table with the referenced primary or unique key are being dropped in the sameDROP TABLEstatement, the referencing table must be listed first. ...