用MySQL的存储过程来实现一些经典函数

质数判断

Java原型

boolean isPrime(int n) {
    if (n<2) {return false;}
    else if (n==2) {return true;}
    else if (n%2==0) {return false;}
    else {
        for (int i=3;i<=(int)Math.sqrt(n);i+=2) {
            if (n%i==0) {return false;}
        }
        return true;
    }
}

MySQL实现

# 判断质数
delimiter //

create procedure isprime(n int)
begin
	declare isprime boolean default true;
	declare n_sqrt int default sqrt(n);
	declare i int default 3;
	declare p int default 2; # 因数
	if n<2 then
		set isprime = false;
	elseif n=2 then
		set isprime = true;
	elseif n%2=0 then
		set isprime = false;
	else
		t:while i<n_sqrt do
			if n%i=0 then
				set isprime = false;
				set p = i;
				leave t;
			end if;
			set i = i+2;
		end while t;
	end if;
	if isprime then
		select n,'true' as 'isPrime' from dual;
	else
		select n,'false' as 'isPrime', p from dual;
	end if;
end //

delimiter ;

call isprime(65536); # 测试1
call isprime(2333); # 测试2
drop procedure isprime; #测试完删除存储过程

输出

MariaDB [mydb]> call isprime(65536);
+-------+---------+------+
| n     | isPrime | p    |
+-------+---------+------+
| 65536 | false   |    2 |
+-------+---------+------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.04 sec)

MariaDB [mydb]> call isprime(2333);
+------+---------+
| n    | isPrime |
+------+---------+
| 2333 | true    |
+------+---------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.04 sec)

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未完待续