mysql basic character function

# View the current character set

SHOW VARIABLES LIKE '%char%';

# One-way function

MyEmployees the USE;
# character function

SELECT LENGTH('哈哈') #获取参数字节个数
SELECT CONCAT(last_name,'_',first_name) FROM employees; #字符串拼接
SELECT UPPER('aaa');  #转换成大写
SELECT LOWER('AAA');  #转换成小写

#mysql index position from the beginning, and substring effect as sbstr

SELECT SUBSTR('李莫愁爱上了陆展元',7); #截取陆展元字符串,从7开始到之后所有
SELECT SUBSTR('李莫愁爱上了陆展元',1,3);#截取李莫愁,第二个数字表示长度

SELECT INSTR('杨不悔爱上了殷六侠','殷六侠') AS out_put;#返回子字符串在大字符串中第一次出现的起始索引位置，没有返回0

SELECT TRIM('    张翠山   ') AS out_put;  #去掉前后空格
SELECT TRIM('a' FROM 'aaaaa张aaa翠aaaaa山aaaaaa') AS out_put; #去掉前后指定字符，不能去掉中间的

SELECT LPAD('黄大侠',10,'*') AS out_put; #从左边填充*直到指定长度10，字符串超过指定长度，会截断为指定长度
SELECT RPAD('黄大侠',10,'*') AS out_put; #从右边填充*直到指定长度10

SELECT REPLACE('张无忌爱上了周芷若','周芷若','赵敏') AS out_put; #替换字符串内的所有周芷若为赵敏，不是一个

# Case: name uppercase, lowercase name, and then stitching

SELECT CONCAT(UPPER(last_name),'_',LOWER(first_name)) FROM employees;