Relationship between characters and mathematical functions

select charset('你好')；
select concate('nihao', 'mysql','java');
select concat('你好')；
select instr('www.baidu.com', 'baidu');
Select ucase('abc');
Select lcase('ABC');
Select left('abcdefg',3);
Select length('abc');
select replace('www.baidu.com', 'baidu', 'qq');
select strcmp('abc','abc');
select strcmp('abc','ABC');
select substring('www.baidu.com ',3,5);
select ltrim(' abc');
select rtrim(' abc');
select length rtrim(' abc');
select length (rtrim(' abc'));
select abs(1);select abs(-1);
select bin(3);select ceiling(1.1);
select floor(1.1);
select conv(10, 10, 2);
select format(2.222333, 0);
select hex(10);
select least(2, 4, 5, 6, 10);
select mod(10, 3) ;
select rand(0,10);