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Can one primary key have two foreign keys in same table?
It is logically right in database management and in fact possible and must be allowed by any RDBMS to reference a foreign key to two or more tables that wants it’s primary key as a foreign key in a given table.
What happens to the data of a table with foreign keys when the associated table with primary keys has been updated?
No the foreign key is not updated automatically. You need to update the foreign key in the tables in which it is referenced by yourself else it would result in referential integrity exception. For updating the foreign key automatically you may use TRIGGERS.
How to make two foreign keys on the same table?
So I made two foreign keys that reference to the primary key of the same table. If a row is the first in the chronological order, the value of the previous element would be null. calendars ——– calendar_id (PRIMARY KEY) calendar_prev calendar_next other columns…
Is there a FOREIGN KEY constraint for owner _ ID?
Owner_ID would not have a foreign key constraint but would be used as a reference to the other tables. The downside is that you would have to look at the table to see what the owner types there are since it isn’t immediately obvious based upon the schema.
How to set up primary and foreign keys referencing two?
Msg 142, Level 15, State 2, Line 2 Incorrect syntax for definition of the ‘TABLE’ constraint. Please advise. The actual error message you are getting is because your CREATE TABLE statement is malformed as you cannot have a foreign key refer to more than one table.
How to null a foreign key in SQL Server?
[User] (ID), Subject varchar (50) NULL, CONSTRAINT CK_Ticket_GroupUser CHECK ( CASE WHEN OwnerGroup IS NULL THEN 0 ELSE 1 END + CASE WHEN OwnerUser IS NULL THEN 0 ELSE 1 END = 1 ) ); As you can see, the Ticket table has two columns, OwnerGroup and OwnerUser, both of which are nullable foreign keys.