- How to create a foreign key in phpmyadmin - Stack Overflow
CREATE TABLE products( prd_id int not null auto_increment primary key, prd_name varchar(355) not null, prd_price decimal, cat_id int not null, FOREIGN KEY fk_cat(cat_id) REFERENCES categories(cat_id) ON UPDATE CASCADE ON DELETE RESTRICT )ENGINE=InnoDB; Create a vendors table and modify products table:
- Differences between foreign key and constraint foreign key
CREATE TABLE Orders ( O_Id int NOT NULL, OrderNo int NOT NULL, P_Id int, PRIMARY KEY (O_Id), CONSTRAINT fk_PerOrders FOREIGN KEY (P_Id) REFERENCES Persons(P_Id) ) Also, from CREATE TABLE (Transact-SQL) one can see that [ CONSTRAINT constraint_name ] is optional
- What is a proper naming convention for MySQL FKs?
user_id in messages table is a fk field so it has to make clear which id is (user_id) a fully-self-explaining naming convention, in my opinion, could be: fk_[referencing table name]_[referencing field name]_[referenced table name]_[referenced field name] i e : `fk_messages_user_id_users_id`
- foreign key constraint naming scheme - Stack Overflow
FK_task_user This gives you an 'at a glance' view of which tables are involved in the key, so it makes it easy to see which tables a particular one (the first one named) depends on (the second one named) In this scenario the complete set of keys would be: FK_task_user FK_note_task FK_note_user
- Does a foreign key automatically create an index?
However, it makes a lot of sense to index all the columns that are part of any foreign key relationship An FK-relationship will often need to look up a relating table and extract certain rows based on a single value or a range of values So it makes good sense to index any columns involved in an FK, but an FK per se is not an index
- List of foreign keys and the tables they reference in Oracle DB
WITH reference_view AS (SELECT a owner, a table_name, a constraint_name, a constraint_type, a r_owner, a r_constraint_name, b column_name FROM dba_constraints a, dba_cons_columns b WHERE a owner = b owner AND a constraint_name = b constraint_name AND constraint_type = 'R'), constraint_view AS (SELECT a owner a_owner, a table_name, a column_name
- How can I find out what FOREIGN KEY constraint references a table in . . .
I am trying to drop a table but getting the following message: Msg 3726, Level 16, State 1, Line 3 Could not drop object 'dbo UserProfile' because it is referenced by a FOREIGN KEY constraint
- Is it fine to have foreign key as primary key? - Stack Overflow
It is possible to only have a FK in a table and still get unique values You can use a column that has classes that can only be assigned one at a time The column would work almost like a unique ID, if you want a unique category value that distinguishes each record
|