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, ...
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...
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 ...
ADD [ COLUMN ] column_type [ column_constraint [ ... ] ] DROP [ COLUMN ] column [ RESTRICT | CASCADE ] ALTER [ COLUMN ] column TYPE type [ USING expression ] ALTER [ COLUMN ] column SET DEFAULT expression ALTER [ COLUMN ] column DROP DEFAULT ALTER [ COLUMN ] column { SET | DROP...
外键默认名称为 tablename_columnname_fkey "CONSTRAINT skills_Userid_fkey" 可省略。CREATE TABLE IF NOT EXISTS skills( Id serial, Userid integer NOT NULL, Name VARCHAR(10) NOT NULL, CreatedAt timestamptz DEFAULT current_timestamp, UpdatedAt timestamptz DEFAULT current_timestamp, CONSTRAINT skills_...
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); ...
# 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) ); # many2many,添加一个中间表 order_items 来引用两个主表 products 和...
ADD CONSTRAINT <foreign key constraint> FOREIGN KEY (<foreign_key_field>)REFERENCES <parent_table>(<primary key field>)...同样增加maintenance_work_mem配置参数也能提高重新创建外键约束的性能。暂停触发器 INSERT或DELETE触发器（如果导入过程还涉及从目标表中删除记录）可能会导致批量数据导入延迟。这是因为...
ALTERTABLEproductsADDCOLUMNdescription textCHECK(description<>''); 二、删除列 要删除列,请使用如下命令: ALTERTABLEproductsDROPCOLUMNdescription; 列中的任何数据都会消失。涉及列的表约束也被删除。但是,如果该列被另一个表的外键约束引用,PostgreSQL 不会默默地删除该约束。您可以通过添加 CASCADE 来授权删除依赖于...
ALTER TABLE partitioned_table ADD CONSTRAINT fk_constraint FOREIGN KEY (column_name) REFERENCES referenced_table (column_name); 在上面的示例中,partitioned_table是分区的主表,column_name是主表中要引用的列名,fk_constraint是外键约束的名称,referenced_table是被引用的表,column_name是被引用表中的列...