Understanding NATURAL JOIN and Why It Is Discouraged
A NATURAL JOIN automatically joins tables using all columns that have the same name in both tables. You do not specify the join condition — MySQL determines it for you based on column names.
• MySQL looks for columns with the same name in both tables.
• It automatically creates an equality condition using those columns.
• It removes duplicate columns from the output.
• You do not write an ON clause.
• Implicit join conditions — You cannot see which columns are being used for the join.
• Schema changes can silently break the query (e.g., adding a column with the same name unintentionally changes the join).
• Hard to debug because the join logic is hidden.
• Unpredictable behavior if multiple columns share the same name.
• Less readable and not obvious to other developers.
• Use explicit JOIN ... ON clauses.
• Clearly specify which columns should be matched.
• Provides full control and avoids unpredictable joins.
In summary: NATURAL JOIN works automatically based on column names, but its implicit behavior makes it risky, unpredictable, and difficult to maintain — which is why it is discouraged in production code.