• 示例：在查询中使用带搜索条件的 CASE 表达式
    2. Query OK, 0 rows affected (0.07 sec)
    4. obclient> INSERT INTO t_case2(id,c_date) 
    5. VALUES (1,to_date('2019-03-01','yyyy-mm-dd'))
    6.      ,(2,to_date('2019-05-08','yyyy-mm-dd'))
    7.      ,(3,to_date('2019-07-07','yyyy-mm-dd'))
    8.      ,(4,to_date('2019-10-11','yyyy-mm-dd'))
    9.      ,(5,to_date('2019-12-12','yyyy-mm-dd'))
    10.      ,(6,to_date('2020-01-05','yyyy-mm-dd'));
    11. Query OK, 6 rows affected (0.01 sec)
    13. obclient> SELECT id, c_date,
    14.      CASE
    15.          WHEN months_between(sysdate, c_date) > 12 THEN 'More than one year ago'
    16.          WHEN months_between(sysdate, c_date) > 9 THEN 'More than three quarters ago'
    17.          WHEN months_between(sysdate, c_date) > 6 THEN 'More than half a year ago'
    18.          WHEN months_between(sysdate, c_date) > 3 THEN 'More than a quarter ago'
    19.          WHEN months_between(sysdate, c_date) >= 0 THEN 'Within a quarter'
    20.          ELSE 'Illegal'
    21.      END "Duration"
    22.  FROM t_case2;
    24. | ID | C_DATE    | Duration                     |
    25. +----+-----------+------------------------------+
    26. |  1 | 01-MAR-19 | More than one year ago       |
    27. |  2 | 08-MAY-19 | More than three quarters ago |
    28. |  3 | 07-JUL-19 | More than half a year ago    |
    29. |  4 | 11-OCT-19 | More than a quarter ago      |
    30. |  5 | 12-DEC-19 | More than a quarter ago      |
    31. |  6 | 05-JAN-20 | Within a quarter             |
    32. +----+-----------+------------------------------+
    33. 6 rows in set (0.00 sec)