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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
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
Can a foreign key be NULL and or duplicate? - Stack Overflow Most FKs are for a one to many relationship and that is what you get from a FK without adding a further constraint on the field So you have an order table and the order details table for instance If the customer orders ten items at one time, he has one order and ten order detail records that contain the same orderID as the FK
sql - Foreign Keys vs Joins - Stack Overflow @Kangkan creating FK have nothing to do with performance FK != Indexes There are DBMS automatic creates a index in the FK creation but most don't Joins don't need FK please refer to excellent Daniel answer Maybe OP is confused by ORM frameworks –
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`
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 drop a foreign key in SQL Server? - Stack Overflow The object 'Company_CountryID_FK' is dependent on column 'CountryID' Msg 4922, Level 16, State 9, Line 2 ALTER TABLE DROP COLUMN CountryID failed because one or more objects access this column I have tried this, yet it does not seem to work: alter table company drop foreign key Company_CountryID_FK; alter table company drop column CountryID;
INSERT statement conflicted with the FOREIGN KEY constraint - SQL . . . The way a FK works is it cannot have a value in that column that is not also in the primary key column of the referenced table If you have SQL Server Management Studio, open it up and sp_help 'dbo Sup_Item_Cat' See which column that FK is on, and which column of which table it references You're inserting some bad data
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