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, ...
Summary: in this tutorial, you will learn about the PostgreSQL foreign key and how to add foreign keys to tables using foreign key constraints. Introduction to PostgreSQL Foreign Key Constraint In PostgreSQL, a foreign key is a column or a group of columns in a table that uniquely identifies ...
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, c) REFERENCES other_table (c1, c2) ); # many2man...
CREATE TABLE table1 ( id SERIAL PRIMARY KEY, column1 VARCHAR(50), column2 INTEGER, FOREIGN KEY (column2) REFERENCES table2(id) ); ``` 2、如果表已经创建,可以使用ALTER TABLE语句添加外键约束,如下所示: ```sql ALTER TABLE table1 ADD CONSTRAINT fk_column2 FOREIGN KEY (column2) REFERENCES t...
{ UNIQUE ( column_name [, ... ] ) [ USING INDEX TABLESPACE tablespace ] | PRIMARY KEY ( column_name [, ... ] ) [ USING INDEX TABLESPACE tablespace ] | CHECK ( expression ) | FOREIGN KEY ( column_name [, ... ] ) REFERENCES ref_table [ ( ref_column [, ... ] ) ] ...
ALTER [ COLUMN ] 字段名 SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN } ADD 表约束 DROP CONSTRAINT 约束名字 [ RESTRICT | CASCADE ] CLUSTER ON 索引名称 SET WITHOUT CLUSTER SET WITHOUT OIDS OWNER TO 新属主 SET TABLESPACE 表空间名字 ...
foreign key("UserId") references "SysUser"("UserId") ); --说明:外键默认名称为tablename_columnname_fkey 1. 2. 3. 4. 5. 6. 7. 8. 9. 3.通过修改表结构设置外键 --语法:alter table table_name add [constraint constraint_name] foreign key(column_1) references TableName(ColumnName); ...
CREATE INDEX <index_name> ON <target_table>(column1, …,column n)创建索引之前，临时提高maintenance_work_mem配置参数可能会有帮助。增加的工作内存可以帮助更快地创建索引。为了安全起见的另一种选择是使用现有数据和索引在同一数据库中复制目标表。然后，测试有索引和删除索两种情况下批量导入数据的性能对比，...
67CASCADE8级联删除或更新。分别删除一个引用行或者更新一个引用列的值。910SETNULL11当引用列删除,设置引用列(referencingcolumn(s))的值为null1213SETDEFAULT14设置引用列为其缺省值。如果缺省值不是null,那么仍然需要被引用表中有一条记录的被引用字段的值与之匹配,否则操作会失败。
JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name WHERE constraint_type = 'FOREIGN KEY'; 2. 根据外键名称,查找其对应的主键表名。在查询结果中,外键表名可以通过tc.table_name获取,主键表名可以通过ccu.table_name获取。发布...