Commas or JOIN Clauses in MySQL: Which Join Syntax Should You Use?

Commas vs. Join Clauses: Understanding the Nuances in MySQL

In MySQL, when joining tables, you have two options: comma-separated joins and join clauses. Both methods can produce the same results, but there are subtle differences that may influence your choice.

Consider a scenario where you have two tables, "Person" and "Worker," with an "id" column in each that relates them. When querying these tables, you may use two syntax options:

SELECT * 
FROM Person, 
     Worker 
WHERE Person.id = Worker.id;

Or,

SELECT * 
FROM Person 
JOIN Worker 
ON Person.id = Worker.id;

The above queries both return the same results. However, there is a crucial distinction between the two approaches.

In the first query, the tables are joined using commas. This syntax is considered deprecated and less readable. Additionally, it can become cumbersome when joining multiple tables.

In contrast, the second query uses an explicit join clause (JOIN ... ON ...). This approach is preferred for its clarity and flexibility. It allows you to specify the join condition more explicitly, making it easier to understand and maintain.

Therefore, while both syntax options can produce the same results, the join clause syntax is generally favored due to its improved readability and maintainability.

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