CREATE TABLE orders ( order_id integer PRIMARY KEY, product_no integer REFERENCES products, quantity integer ); # 定义多个 Column 组成的外键,要求被约束列(外键)的数量和类型应该匹配被引用列(主键)的数量和类型。 CREATE TABLE t1 ( a integer PRIMARY KEY, b integer, c integer, FOREIGN KEY (b, ...
test=#altertabletbl_foreigndropconstraintfk_tbl_foreign_a_b ;ALTERTABLEtest=#deletefromtbl_foreign;DELETE2test=#insertintotbl_foreign(a,b)values(1,2),(2,2),(1,1);INSERT03test=#insertintotbl_foreign(a)values(3),(4);INSERT02test=#insertintotbl_foreign(c)values(5);INSERT01test=#select*...
--语法:alter table table_name add [constraint constraint_name] foreign key(column_1) references TableName(ColumnName); create table "SysUserInfo"( "UserId" integer, "RealName" varchar(50), "IdCard" varchar(50), "Gender" smallint, primary key("UserId") ); alter table "SysUserInfo" add...
referential_action in a FOREIGN KEY/REFERENCES constraint is: { NO ACTION | RESTRICT | CASCADE |SETNULL [ ( column_name [, ... ] ) ] |SETDEFAULT [ ( column_name [, ... ] ) ] } URL: https://www.postgresql.org/docs/16/sql-altertable.html postgres=# 删除表命令 命令 1 2 3 4 ...
sql`ALTER TABLE table_name ADD CONSTRAINT constraint_name FOREIGN KEY (column1, column2, ...) REFERENCES referenced_table (column1, column2, ...);``` 其中,`table_name`是表名,`constraint_name`是外键约束名,`column1, column2, ...`是外键涉及的列名,`referenced_table`是被引用的表名,`colu...
通常一个表中的 FOREIGN KEY 指向另一个表中的 UNIQUE KEY(唯一约束的键),即维护了两个相关表之间的引用完整性。 实例 下面实例创建了一张 COMPANY6 表,并添加了5个字段: CREATE TABLE COMPANY6( ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL, ...
alter table orders add constraint orders_product_no_fkey foreign key ("product_no") references products("product_no"); 删除外键约束 如果要删除外键约束,则可以执行以下命令: alter table orders drop constraint orders_product_no_fkey; 总结 外键主要控制存储在外键表中的数据,用来和其他数据表建立联系,...
PostgreSQL Alter Table Exercises: Write a SQL statement to add a foreign key constraint named fk_job_id on job_id column of job_history table referencing to the primary key job_id of jobs table.
问Postgresql:更改外键约束的操作EN外键约束 foreign key 外键约束的要求： 父表和字表必须使用相同的...
"t_pkey"PRIMARY KEY, btree(id) postgres=# 添加外键 create table t_p(f1 int not null,f2 int ,primary key(f1)); create table t_f(f1 int not null,f2 int); postgres=# ALTER TABLE t_f ADD CONSTRAINT t_f_f1_fkey FOREIGN KEY (f1) REFERENCES t_p (f1); ...