MySQL 提供了丰富的内置函数,主要分为以下几大类:一、字符串函数CONCAT()拼接字符串SELECT CONCAT('Hello', ' World'); → Hello WorldSUBSTRING()截取字符串SELECT SUBSTRING('abcdef', 2, 3); → bcdUPPER() / LOWER()转换大小写SELECT UPPER('hello'); → HELLOTRIM()去除空格SELECT TRIM(' hello '); → helloREPLACE()替换字符串SELECT REPLACE('hello world', 'world', 'MySQ...