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...
= 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> [ ,... ...
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 /...
24-SQL FOREIGN KEY 约束 SQL FOREIGN KEY 约束一个表中的FOREIGN KEY(外键) 指向另一个表中的PRIMARY KEYSQL FOREING KEY Constraint on CREATE TABLESQL FOERIGN KEY Constraint on ALTER TABLE"Orders"表中的“Id_P”列指向"Persons"表中的“Id_P”列“Persons”表中的“Id_P”列是“Persons”表中的PRIM...
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...
首先,在CONSTRAINT关键字之后指定外键约束名称。约束名称是可选的,可以不写,因此可以按如下方式定义外键约束: FOREIGNKEY (column_1, column2,...) REFERENCESparent_table_name(column1,column2,..) 这样就没有指定外键约束的名字,这种情况下,SQL Server会自动给FOREIGN KEY约束生成一个名字。
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])] ...