Comma-Separated Joins vs. JOIN ON in MySQL: What's the Real Difference?

Understanding the Difference between Comma Separated Joins and JOIN ON Syntax in MySQL

The question arises when dealing with database tables with related columns, particularly when using MySQL. Two common syntaxes for joining tables are the comma-separated join and the JOIN ON syntax.

Comma-Separated Joins

The comma-separated join, resembling SELECT * FROM Person, Worker WHERE Person.id = Worker.id, joins tables by matching rows based on a common column or columns. However, this syntax has been deprecated in MySQL in favor of the JOIN ON syntax.

JOIN ON Syntax

The JOIN ON syntax, as seen in SELECT * FROM Person JOIN Worker ON Person.id = Worker.id, explicitly specifies the columns that should be used for joining the tables. This syntax is more precise, provides enhanced readability, and is widely used in modern MySQL queries.

Difference

Surprisingly, there is no functional difference between comma-separated joins and JOIN ON syntax in MySQL. Both result in the same joined table. The use of the JOIN ON syntax is simply a matter of readability and it's considered good programming practice in MySQL.

In summary, although the comma-separated join is still technically valid in MySQL, it's recommended to adopt the JOIN ON syntax for clarity and conformity with modern MySQL conventions.

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