How to Create Efficient Composite Primary Keys in MySQL for Relational Database Design?

Creating Composite Primary Keys in MYSQL

In complex database setups, it becomes necessary to establish relationships between tables effectively. Composite primary keys offer a robust solution when multiple columns are required to uniquely identify records across multiple tables. This article explores the creation of composite primary keys in MYSQL and examines various options for representing the key values.

Consider a scenario with three tables: table_1, table_2, and info. The first two tables have auto-increment surrogate primary keys, while info contains information that relates to both table_1 and table_2. The task is to determine the appropriate representation of a composite primary key for info that combines the IDs from both table_1 and table_2.

Various options for representing the composite key are available:

• INT (9) 11209437: While simple, this format can be problematic for large numbers.
• VARCHAR (10) 11209-437: This is a human-readable representation but is less efficient for MySQL.
• DECIMAL (10,4) 11209.437: While accurate, it may be overkill for the intended purpose.

The recommended approach is to use a composite (multi-column) key, as seen in the following example:

This structure not only provides a unique identifier for each record in info but also establishes foreign key relationships with table_1 and table_2. Additionally, this representation is optimized for MySQL's data handling capabilities.

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