What is the difference between these three MySQL queries?

Question

SELECT title,name FROM Lessons,Users WHERE Lessons.author = Users.email;

and

SELECT title,name FROM Lessons JOIN Users ON Lessons.author = Users.email;

and

SELECT title,name FROM Lessons INNER JOIN Users ON Lessons.author = Users.email;

Lessons has a column named author indexed as a foreign key to a Users.email. title is a column in Lessons and name is a column in Users

Answer 1

There is no difference between the three statements, they all are, either implicit or explicit, INNER JOINs

1. The first statement is using the implicit old join syntax. While this is still supported, using explicit joins is both more readable and maintainable. Don't use old style joins.

2. The second statement is using an explicit join without specifying the type of join. By default, this is an INNER JOIN

3. The third statement is also an explicit join and avoids any ambiguities. This is by far the most recommended way of writing joins.