How many times can a foreign key be listed in a table?
Answer: SQL Server 2014 and earlier versions, supports 253 as a maximum foreign key table references per table. However, this limitation, changes in SQL Server 2016. a) Outgoing Foreign Key References – A column in a table referring other table columns.
Can foreign key be duplicate in SQL?
A table is allowed to contain more than one foreign key. Short answer: Yes, it can be NULL or duplicate. By the SQL standard, a foreign key must reference either the primary key or a unique key of the parent table. If the primary key has multiple columns, the foreign key must have the same number and order of columns.
What’s the maximum number of foreign keys in SQL Server?
The recommended limit for the number of foreign keys in a table is 253. See Maximum Capacity Specifications for SQL Server on MSDN. “Although a table can contain an unlimited number of FOREIGN KEY constraints, the recommended maximum is 253.
Is there a maximum number of references to a table in SQL Server?
“Although a table can contain an unlimited number of FOREIGN KEY constraints, the recommended maximum is 253. Depending on the hardware configuration hosting SQL Server, specifying additional FOREIGN KEY constraints may be expensive for the query optimizer to process.”
How many foreign keys can we have for a table?
Nevertheless, the actual number of FOREIGN KEY constraints is limited by your hardware configuration and by the design of your database and application. We recommend that a table contain no more than 253 FOREIGN KEY constraints, and that it be referenced by no more than 253 FOREIGN KEY constraints.
Can a foreign key reference reference another table?
FOREIGN KEY constraints can reference only tables within the same database on the same server. Cross-database referential integrity must be implemented through triggers. For more information, see CREATE TRIGGER. FOREIGN KEY constraints can reference another column in the same table, and is referred to as a self-reference.