oracle中的greatest 函数和 least函数示例代码

SQL> select * from tb;
    ID CHINESE  MATH ENGLISH
 ---------- ---------- ---------- ----------
  1001    89    98    87
  1002    81    87    79 

    ID CHINESE  MATH ENGLISH    MAX    MIN
 ---------- ---------- ---------- ---------- ---------- ----------
  1001    89    98    87    98    87
  1002    81    87    79    87    79

SQL> SELECT id, chinese, math, english,
  2    greatest (chinese, math, english) max,
  3    least(chinese, math, english) min
  4  FROM tb;

    ID CHINESE  MATH ENGLISH    MAX    MIN
 ---------- ---------- ---------- ---------- ---------- ----------
  1001    89    98    87    98    87
  1002    81    87    79    87    79

SQL>SELECT GREATEST(2, 5, 12, 3, 16, 8, 9) A FROM DUAL;   
A
----------   
16

SQL>SELECT GREATEST(2, '5', 12, 3, 16, 8, 9) A FROM DUAL;   
A
----------  
16

SQL>SELECT GREATEST(2, 'A', 12, 3, 16, 8, 9) A FROM DUAL;
SELECTGREATEST(2, 'A', 12, 3, 16, 8, 9) A FROM DUAL

SQL> 
SELECT GREATEST('A', 'B', 'C', 'D', 'E', 'F','G') A FROM DUAL;
A
-
G

SQL> 
SELECT GREATEST('A', 'B', 'C', 'D', 'E','GA', 'GAB') A FROM DUAL;
A
---
GAB

SQL> 
SELECT GREATEST('A', 6, 7, 5000, 'E', 'F','G') A FROM DUAL;
A
-
G

SQL> 
SELECTGREATEST(sysdate,TO_DATE('2014-08-01','YYYY-MM-DD')) A FROM DUAL;
A
-----------
2014/8/1

SQL> 
SELECT GREATEST(sysdate,'2014-08-01') A FROMDUAL;
SELECTGREATEST(sysdate,'2014-08-01') A FROM DUAL

SQL> 
SELECT GREATEST(NULL, 'B', 'C', 'D', 'E','GA', 'GAB') A FROM DUAL;
A
-

SQL> 
SELECT GREATEST('A', 'B', 'C', 'D', 'E',NULL, 'GAB') A FROM DUAL;
A
-