Learn how to add and remove Primary Keys from an Access database table. The primary key's purpose is to promptly associate data from multiple tables and combine that data.

Some database designers may feel that it’s OK to arbitrarily assign all dimensional foreign keys as part of a fact’s primary key even when one or more do not actually contribute to the fact table’s ...

Generated keys can be a useful tool in creating logical database designs, but they can be easily over-used. The designer must consider whether the business truly wishes to drive a function that ...

The column (field) in a relational database that uniquely identifies the row in the table. For example, account number is often a primary key. A "composite primary key" or "super key" is made up ...

All documents in a MongoDB collection have a primary key dubbed _id . This field is automatically assigned to a document upon insert, so there’s rarely a need to provide it. What’s interesting ...

Duplicate and Ignore on MySQL Inserts. MySQL table primary keys and unique indexes prevent multiple rows with the same index from being added to the table. If you try to insert a duplicate row ...

Every JPA entity has a primary key, but some entities have more than one value as their primary key. In this case, you need to use a composite key. This Java tip introduces you to using composite ...