Is it possible to perform table joins if the database does not have a foreign or internal key for data linking?

Yes, joining tables through JOIN is possible even if there are no foreign or primary keys set in the database. JOIN is an SQL operation that links rows from two tables based on a condition specified in the ON clause.

Foreign or primary keys are integrity constraints that help ensure the correctness of relationships, but they are not mandatory for performing a JOIN.

For example, you can execute a query like:

SELECT *
FROM table1 t1
JOIN table2 t2 ON t1.columnA = t2.columnB;

Here, the linking occurs based on matching values in columns, regardless of the presence of keys.

However, the absence of keys can lead to:

• Potential data errors (inconsistencies)
• Decreased query performance

Therefore, it is recommended to use keys to ensure integrity and optimize performance.