Examine these commands which execute successfully:
mYsql> CREATE TABLE income (acct_num INT, amount DECIMAL(10,2));
mysql> CREATE TRIGGER subtotal BEFORE INSERT ON income
FOR EACH ROW SET @subtotal = subtotal + NEW.amount;
Which is true for the income table?

Examine the appointments table definition which contains one million rows:

Now, examine this statement which executes successfully:

Which statement will improve query performance?