- 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`
- 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
- How to find foreign key dependencies in SQL Server?
select fk_table = fk table_name, fk_column = cu column_name, pk_table = pk table_name, pk_column = pt column_name, constraint_name = c constraint_name from information_schema referential_constraints c inner join information_schema table_constraints fk on c constraint_name = fk constraint_name inner join information_schema table_constraints pk
- How do I create a foreign key in SQL Server? - Stack Overflow
Alter Table ForeignKeyTable Add constraint `ForeignKeyTable_ForeignKeyColumn_FK` `Foreign key (ForeignKeyColumn)` references `PrimaryKeyTable (PrimaryKeyColumn)` i e Alter Table tblEmployee Add constraint tblEmployee_DepartmentID_FK foreign key (DepartmentID) references tblDepartment (ID)
- Is it possible to list all foreign keys in a database?
Practically, it depends on how many tables have the FK definitions included If someone bothered to carefully define all FK references -- and the SELECT statements stick to these rules -- you can query them However, since a SELECT statement can join on anything, there's no guarantee that you have all FK's unless you also have all SELECT
- 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
- sql - Foreign Key to non-primary key - Stack Overflow
Consider the case of a Customer table with a SSN column (and a dumb primary key), and a Claim table that also contains a SSN column (populated by business logic from the Customer data, but no FK exists) The design is flawed, but has been in use for several years, and three different applications have been built on the schema
- 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
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