A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. A FOREIGN KEY constraint can contain null values; however, if any column of a composite FOREIGN ...
The CONSTRAINT FK_employee_department specifies the foreign key name FK_employee_department, FOREIGN KEY(dept_id) specifies the foreign key column in the employee table, and REFERENCES department(dept_id) specifies that the foreign key column refers to the dept_id column of the department table....
PT.COLUMN_NAMEASPrimaryKeyColumnFROMINFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS FKINNERJOININFORMATION_SCHEMA.KEY_COLUMN_USAGE CUONFK.CONSTRAINT_NAME=CU.CONSTRAINT_NAMEINNERJOININFORMATION_SCHEMA.KEY_COLUMN_USAGE PTONFK.UNIQUE_CONSTRAINT_NAME=PT.CONSTRAINT_NAMEWHEREPK.TABLE_NAME='YourTableName';-- 替换...
在MySQL执行truncate table xxx时, 出现了这个报错[Err] 1701 -Cannot truncate a table referenced in a foreign key constraint.. 意思是 无法截断外键约束中引用的表 解决办法 mysql中运行SET FOREIGN_KEY_CHECKS=0,删除外键约束 之后执行SET FOREIGN_KEY_CHECKS=1,启动外键约束 在重新truncate table xxx;清空就...
使用truncate截断表速度快,不仅可以清空表数据,而且可以使自增列重新从1开始 二、出现错误的原因 Mysql中如果表和表之间建立了外键约束,则无法删除表及修改表结构 三、解决方案 在Mysql中取消外键约束: SET FOREIGN_KEY_CHECKS=0 执行 truncatetablename
Referred Column:The column name in the referred table. Reference option:These are the actions that come into the picture when an update or delete action is done on the table that holds the foreign key constraint. Both UPDATE and DELETE can have the same or different reference options. ...
SQL FOREIGN KEY Constraint on CREATE TABLE 下面的 SQL 在 "Orders" 表创建时为 "Id_P" 列创建 FOREIGN KEY: MySQL: CREATE TABLE Orders ( Id_O int NOT NULL, OrderNo int NOT NULL, Id_P int, PRIMARY KEY (Id_O), FOREIGN KEY (Id_P) REFERENCES Persons(Id_P) ...
This example illustrates foreign key definition using the SQL Distributed Management Objects (SQL-DMO) Key object. In the example, adding the Key object to the Keys collection creates a FOREIGN KEY constraint on the referenced table. 复制 ' Create a FOREIGN KEY constraint on the ' Northwind.....
drop table if exists tb_role_acl;检查表是否存在，如果存在则删除表，估计你之前已经创建过该表，然后其中涉及到外键，这种情况首先得删除外键约束，然后才能删除表。删除约束的语法如下：alter table 表名称 drop constraint 约束名称
TableTypeColumnType TableTypeDefaultConstraint TableTypeIndex TableTypePrimaryKeyConstraint TableTypePrimaryKeyConstraint.ColumnsRelationship TableTypeUniqueConstraint TableTypeUniqueConstraint.ColumnsRelationship TableValuedFunction TcpProtocolSpecifier 鑲嵌 TimeUnit TriggerType TSqlModel TSqlModelOptions...