-- 字符函数:-- 查询结果姓名小写 select lower(ename), sal, job from emp;-- 查询结果姓名大写 select upper(ename), sal, job from emp;-- 名字5个字符 select ename, sal, job from emp where length(ename)=5;-- 名字前3个字符 select substr(ename, 1,3), sal, job from emp; -- 从第1个开始 select su…