And then the sql than or operator to a higher priority, for example, 1 Or Condition 2 Condition 3 Condition And if the first execution or, 1or2 is then and3
But the fact is 2and3 again or 1, so if you want to 1or2 again and 3 will add 1 or 2 brackets (1 or 2) and 3 on it.
IN operator is used to specify the range of conditions select username from user where id in (1,2,3) This is represented by id can match each username 1,2,3.
or and in operator can accomplish the same task, the open parenthesis is divided into three or like, select username from user where id = 1 or id = 2 or id = 3;
negative condition is not followed, for example
select username from user where id not in (1,2,3); id will not find 1,2,3 username, it would not negate the conditions behind.
