I'm having issues with inner join, why isn't it returning matched rows?

Example:

-- Attempting to INNER JOIN without a matching condition
SELECT A.*, B.* FROM tableA A, tableB B;
Solution:

-- Correct INNER JOIN with matching condition
SELECT A.*, B.* 
FROM tableA A 
INNER JOIN tableB B ON A.id = B.id;
INNER JOIN requires a matching condition to return rows that exist in both tables.

Beginner's Guide to SQL