referenced_table_nameandreferenced_column_nameare the names of the table and the column that theFOREIGN KEYconstraint references Also Read:SQL CREATE TABLE Referencing Columns in Another Table with FOREIGN KEY TheFOREIGN KEYconstraint in SQL establishes a relationship between two tables by linking colum...
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...
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) ) SQL Server / Oracle /...
执行,SQL Server报错如下: 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...
usetest;createtabletest01 ( id1intnotnull, id2intnotnull);createtabletest02 ( id11intnotnull, id22intnotnull);altertabletest01addconstraintpk_id1primarykey(id1); 考虑如下关系 test02表中的id11依赖于test01中的id1,因此为test02创建外键 ...
CREATE TABLE Orders ( OrderID INT UNIQUE NOT NULL, OrderItem VARCHAR, OrderQuantity INT, CustomerNum INT, CONSTRAINT OrdersPK PRIMARY KEY (OrderID), CONSTRAINT CustomersFK FOREIGN KEY (CustomerNum) REFERENCES Customers (CustID) ) 最常见的情况是,外键引用另一个表的主键字段。但是,外键可以引用RowID...
= column_set_name XML COLUMN_SET FOR ALL_SPARSE_COLUMNS <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ ,... n ] ) [ WITH FILLFACTOR = fillfactor | WITH ( <index_option> [ ,... ...
To create a FOREIGN KEY constraint on the "P_Id" column when the "Orders" table is already created, use the following SQL:MySQL / SQL Server / Oracle / MS Access:ALTER TABLE Orders ADD FOREIGN KEY (P_Id) REFERENCES Persons(P_Id)...
Truncate Table Create Table 创建表 CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name -- (Note: TEMPORARY available in Hive 0.14.0 and later) [(col_name data_type [COMMENT col_comment], ... [constraint_specification])] ...
ALTER TABLE student DROP CONSTRAINT pk_studentid <!--为没有添加外键的表添加外键,这里是添加多个外键的例子--> ALTER TABLE student ADD CONSTRAINT fk_students FOREIGN KEY (t_id) REFERENCES teachers(t_id) <!--为已经添加“有名字的”外键的表删除外键,这里删除的名为fk_students的外键--> ...