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
-