SELECT substr('abc' ,2, 1) FROM dual --截取字符串
SELECT upper('aa' ) FROM dual --转大写字母
SELECT lower('ACB' ) FROM dual --转小写字母
截取字符串后5位字符
SELECT substr('aabcdefg' ,length('aabcdefg')- 4,5 ) FROM dual
SELECT substr('abc' ,2, 1) FROM dual --截取字符串
SELECT upper('aa' ) FROM dual --转大写字母
SELECT lower('ACB' ) FROM dual --转小写字母
截取字符串后5位字符
SELECT substr('aabcdefg' ,length('aabcdefg')- 4,5 ) FROM dual