MySQL winter vacation self-study 2022 12 (4)

-- 9, Returns the last few characters of a string 
select right('hello',3);  #llo

-- 10, String comparison 
select strcmp('hello','world'); #-1
select strcmp('aaa','aaa'); # 0
select strcmp('aaad','aba'); #-1
select strcmp('b','a'); #1

-- 11, String interception 
select substr('hello',2,3); #ell
select substring('hello',2,3); #ell

-- 12, Convert lowercase to uppercase 
select ucase('helloWorld');#HELLOWORLD
select upper('helloWorld');

-- 13, Change upper case to lower case 
select lcase('HELLOworld');#helloworld
select lower('HELLOworld');