A natural join:
Is a special case of an equijoin; it compares all the columns in one table with corresponding columns that have the same name in the other table for equality.
Works only if the input tables have one or more pairs of meaningfully comparable, identically named columns.
Performs joins implicitly. Don’t specify an ON or USING clause in a natural join.
Is a syntactic convenience that always can be replicated explicitly with an ON clause in JOIN syntax or a WHERE clause in WHERE syntax.
SELECT columns FROM table1 NATURAL JOIN table2