rails generate migration AddForeignKeyToModel 代码语言:txt 复制 打开生成的迁移文件,可以在db/migrate目录下找到该文件,文件名类似于timestamp_add_foreign_key_to_model.rb。 在迁移文件中,使用add_foreign_key方法来添加外键约束。例如,如果要向posts表中的user_id
ALTER TABLE orders ADD CONSTRAINT fk_customer FOREIGN KEY (customer_id) REFERENCES customers(id); 在这个例子中,fk_customer是外键约束的名称,customer_id是orders表中的外键列,它引用了customers表的id列。 3. 执行SQL语句以在数据库中创建外键 执行上述SQL语句后,PostgreSQL数据库将创建相应的外键约束。你可...
constraint student_table3_ibfk_1 foreign key(java_teacher_name,java_teacher_pass) references teacher_table3(teacher_name,teacher_pass) ); #删除foreign key alter table student_table3 drop foreign key student_table3_ibfk_1; #修改表结构时增加foreign key alter table student_table3 add foreign key...
3,增加约束 ALTER TABLE products ADD CHECK (name <> ''); ALTER TABLE products ADD CONSTRAINT some_name UNIQUE (product_no); ALTER TABLE products ADD FOREIGN KEY (product_group_id) REFERENCES product_groups; 要增加一个不能写成表约束的非空约束,使用下面语法: ALTER TABLE products ALTER COLUMN p...
altertablegoodsaddprimarykey(sid); AI代码助手复制代码 (2)、 添加外键 altertableordersaddforeignkey(goods_id)referencesgoods(sid)onupdatecascadeondeletecascade; AI代码助手复制代码 on update cascade:被引用行更新时,引用行自动更新; on update restrict:被引用的行禁止更新; ...
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); ...
enable/disable fk的写法不能用了。。。 网上搜了一下,ms只能用先删除外键,然后重新创建的方式,memo一下。 alter table xxxxx drop constraint xxxx_fk; alter table xxxxx add constraint xxxx_fk foreign key (column1) references yyyyyy (column1);...
多对多关系表的三种创建方式 1.全自动,Django自动创建 class Book(models.Model): title = models.CharField(max_length=20)...全部由orm创建,内置了四个操作第三张表的方法add、remove、set、clear #不足:可扩展性差,自动创...
postgreSQL数据库默认⽤户postgres常⽤命令分享 1、修改⽤户postgres的密码 #alter user postgres with password ‘xxxx';(其中xxxx是修改的密码)。2、查看下当前schema的所有者：// 查看当前schema的所有者，相当于\du元命令 SELECT n.nspname AS "Name",pg_catalog.pg_get_userbyid(n.nspowner) AS "...
ADD FOREIGN KEY — Isn't supported if current user doesn't have permission to read the referenced table or if the referenced table has RLS restrictions enabled that the current user can't bypass. The following example fails because it tries to add a constant value of type timestamp onto a...