substr函数

---取1到3位
SQL> select job,substr(job,1,3) from emp;

JOB	  SUBSTR
--------- ------
CLERK	  CLE
SALESMAN  SAL
SALESMAN  SAL
MANAGER   MAN
SALESMAN  SAL
MANAGER   MAN
MANAGER   MAN
ANALYST   ANA
PRESIDENT PRE
SALESMAN  SAL
CLERK	  CLE

JOB	  SUBSTR
--------- ------
CLERK	  CLE
ANALYST   ANA
CLERK	  CLE

14 rows selected.


---取后2位
SQL>  select job,substr(job,length(job)-1,length(job)) from emp;

JOB	  SUBSTR(JOB,LENGTH(
--------- ------------------
CLERK	  RK
SALESMAN  AN
SALESMAN  AN
MANAGER   ER
SALESMAN  AN
MANAGER   ER
MANAGER   ER
ANALYST   ST
PRESIDENT NT
SALESMAN  AN
CLERK	  RK

JOB	  SUBSTR(JOB,LENGTH(
--------- ------------------
CLERK	  RK
ANALYST   ST
CLERK	  RK

14 rows selected.