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Mysql automatically updating foreign keys

Maybe with the first-class replication in the 9.0 release, it will happen sooner rather than later.

A primary key provides a mechanism for ensuring that the rows in a table are unique.

The values contained in the column or columns that make up the primary key serve to identify each of those rows.

Otherwise, they serve very different purposes and each is governed by its own set of rules.

That said, they can often be related to each other in very important ways, but they still remain separate entities.

My SQL still doesn’t have deferred foreign key constraints, Postgre SQL has had them for as long as I’ve used it. Deferred unique constraints are similar, but mean you can temporarily violate a unique constraint, as long as you clean things up before the transaction commits.

E.g.: to the new value, and have your ORM auto-flush. My SQL doesn’t have deferred unique constraints, Postgre SQL just got them in (the nearly released) 9.0.

There are many differences between primary keys and foreign keys.

In fact, the only real similarity is that you can define each of them on one or more columns in a SQL Server table.

If you want to use Foreign Keys in Mysql, you need to use Inno DB.

The following is a simple example that illustrates Foreign Key constraints, we'll create tables to store information about Authors and their Books. Note, that in My SQL we need to use the Inno DB storage engine to support Foreign Key Constraints.

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