INNER JOIN: Returns the presence of at least one matching row in the table. If no line is not returned rows. (Want to have a result, two conditions must be established in the table)
LEFT JOIN keyword from the left table (table1) returns all rows, even if the right table (table2) does not match. If there is no match in the right table, the result to NULL.
RIGHT JOIN right keyword table (table2) returns all rows, even if the left table (table1) does not match. If there is no match left table, the result is NULL.
FULL OUTER JOIN keyword as long as there is a match left table (table1) and the right table (Table2) wherein a table, the row is returned.