Is start transaction always needed with Mariadb storedprocedure?

I have a mariadb database and a stored procedure. If a select statement is true then a delete query is done. Like this:

  START TRANSACTION;

  # Test if category is in use by a product and IN_category_uuid is an input variable
  IF ((SELECT COUNT(id) FROM products WHERE categoryId = IN_category_uuid) = 0) THEN
    DELETE FROM category WHERE id = IN_category_uuid;

    COMMIT;

    SET OUT_result = 0;
  ELSE
    ROLLBACK;

    SET OUT_result = 2;
  END IF;

My question is, do I need to place the start transaction at the beginning before the select statement or is the following possible?

  # Test if category is in use by a product
  IF ((SELECT COUNT(id) FROM products WHERE categoryId = IN_category_uuid) = 0) THEN
    START TRANSACTION;

    DELETE FROM category WHERE id = IN_category_uuid;

    COMMIT;

    SET OUT_result = 0;
  ELSE
    SET OUT_result = 2;
  END IF;

This second code doesn’t require a rollback and only does a start transaction when a alter command is done.

Answer

Why use an IF? Just write this as:

DELETE FROM category
    WHERE id = IN_category_uuid AND
          NOT EXISTS (SELECT 1 FROM products p WHERE p.categoryId = IN_category_uuid);

You probably don’t need to wrap this in a transaction, but that might depend on the settings for the database. In general, a single command will be in its own transaction (and there is not much to rollback, actually).