SELECT upper('abc') FROM dual;SELECT lower(emp.ename) FROM emp;TRIM(x),LTrim(x),Rtrim(x)--取子串SELECT substr('123456789',7) FROM dual;SELECT substr('123456789',2,1) FROM dual;--取位置SELECT instr('123456789','56') FROM dual;SELECT instr('1234123123','123',3) FROM dual;SELECT instr('1234123123','123',3,2) FROM dual;--判断一个字符串是否在另一个字符串SELECT instr('123456789','a') FROM dual;--填充字符串--添加学生，学号=2位年份+班级号+4位流水号,业务主键--0955 0001,0955 0022,0955 0456SELECT Lpad(1,4,0) FROM dual;SELECT to_char(SYSDATE,'yy') FROM dual;SELECT to_char(SYSDATE,'yy')+'55'+Lpad(16,4,0) FROM dual;--错误SELECT to_char(SYSDATE,'yy')||'55'||Lpad(16,4,0) FROM dual;SELECT to_char(SYSDATE,'yy')||'55'||Lpad(seq1.nextval,4,0) FROM dual;SELECT Lpad(99999,4,0) FROM dual;SELECT Rpad(1,4,0) FROM dual;--工作中几乎不用--b的理解SELECT length('我好你好大家好') FROM dual;--字的个数SELECT lengthB('我好你好大家好') FROM dual;--字的字节数
