Comma vs. JOIN in MySQL: What's the Difference in Syntax and Performance?

Distinct Syntax, Identical Outcomes: Exploring Comma Separated and Join Syntax in MySQL

In MySQL, we commonly encounter two syntaxes for performing joins between tables: comma-separated joins and join on syntax. Although these syntaxes yield equivalent results, their underlying mechanisms and readability differ.

Comma Separated Joins:

In a comma-separated join, multiple tables are listed after the FROM clause, separated by commas. Each table can be aliased using the AS keyword to simplify references. A join condition is then specified using the WHERE clause. Here's an example:

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

Join On Syntax:

In join on syntax, the JOIN keyword is used to explicitly specify the join condition between two tables. The ON keyword follows JOIN and is used to connect the join columns. Here's an example:

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

Difference Explained:

The primary difference between these syntaxes is purely syntactic. Both syntaxes perform an inner join based on the specified join condition. There is no functional or performance difference between them.

Usage Recommendation:

The choice between comma-separated joins and join on syntax is a matter of preference. The join on syntax is considered more explicit and easier to read, especially for complex joins. However, comma-separated joins can sometimes improve readability in simpler cases by allowing you to align the join condition with the table names.

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