How to Design a Composite Primary Key for Relational Database Tables in MySQL?

Creating Composite Primary Keys in MySQL

Composite primary keys play a crucial role in managing relationships between multiple tables. Consider the following scenario:

table_1 (id, field)
table_2 (id, field, field)
info ( ???, field)

The info table contains information related to both table_1 and table_2. It's essential to establish an appropriate primary key for this table.

Composite Primary Keys

The optimal solution for the primary key of the info table is a composite of the IDs from table_1 and table_2. By creating a composite key (t1ID, t2ID), you effectively connect the records in the info table to their respective records in table_1 and table_2.

Data Type Considerations

Regarding the data type for the composite primary key, INT is recommended for both t1ID and t2ID. This choice ensures optimal performance and prevents any data truncation or loss of precision.

Usage on MySQL MyISAM Database

Yes, it's perfectly acceptable to use a composite primary key in a MySQL MyISAM database. MyISAM supports composite keys, and they can be indexed to improve query performance.

Foreign Keys

Additionally, by using t1ID and t2ID as foreign keys, you create referential integrity between the info table and table_1 and table_2. This ensures that data remains consistent and accurate across these tables.

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