MySQL Joins: What's the Difference Between Comma-Separated and JOIN ON Syntax?

Differences Between Comma Separated Joins and JOIN ON Syntax in MySQL

MySQL offers two syntaxes for joining tables: comma-separated joins and JOIN ON. Despite concerns regarding their potential differences, these two syntaxes yield identical results.

The following example compares these syntaxes using tables Person and Worker, where Person.id references Worker.id:

**Comma-Separated Join:**
SELECT *
FROM Person
JOIN Worker
ON Person.id = Worker.id;

**JOIN ON Syntax:**
SELECT *
FROM Person,
     Worker
WHERE Person.id = Worker.id;

As you can see, the JOIN ON syntax provides explicit join conditions, while the comma-separated version utilizes implicit conditions.

Identical Results

Note that these queries produce the same results. The comma-separated join is equivalent to the explicit JOIN ON syntax. MySQL automatically handles the join based on the matching columns mentioned in the WHERE clause.

Readability and Clarity

While the results are identical, the JOIN ON syntax offers enhanced readability and clarity. It explicitly states the join condition, making it easier to understand which tables are being joined and on what criteria. This improves query comprehension and maintenance.

In summary, comma-separated joins and JOIN ON syntax in MySQL achieve the same functionality. However, the JOIN ON syntax provides superior readability and clarity, making it the preferred approach for join operations.

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