• 示例：在查询中使用带搜索条件的 CASE 表达式
    2. Query OK, 0 rows affected (0.02 sec)
    4. obclient> CREATE TABLE t_case2(id number NOT NULL PRIMARY KEY, c_date date );
    5. Query OK, 0 rows affected (0.14 sec)
    7. obclient> INSERT INTO t_case2(id,c_date) 
    8. VALUES (1,'2019-03-01')
    9.      ,(2,'2019-05-08')
    10.      ,(3,'2019-07-07')
    11.      ,(4,'2019-10-11')
    13. Query OK, 6 rows affected (0.01 sec)
    14. Records: 6  Duplicates: 0  Warnings: 0
    16. obclient>
    17. obclient> SELECT id, c_date,
    18.      CASE
    19.          WHEN datediff(now(), c_date) > 12*30 THEN 'More than one year ago'
    20.          WHEN datediff(now(), c_date) > 9*30 THEN 'More than three quarters ago'
    21.          WHEN datediff(now(), c_date) > 6*30 THEN 'More than half a year ago'
    22.          WHEN datediff(now(), c_date) > 3*30 THEN 'More than a quarter ago'
    23.          WHEN datediff(now(), c_date) >= 0 THEN 'Within a quarter'
    24.      END "Duration"
    25.  FROM t_case2;
    26. +----+------------+------------------------------+
    27. | id | c_date     | Duration                     |
    28. +----+------------+------------------------------+
    29. |  1 | 2019-03-01 | More than one year ago       |
    30. |  2 | 2019-05-08 | More than three quarters ago |
    31. |  3 | 2019-07-07 | More than three quarters ago |
    32. |  4 | 2019-10-11 | More than a quarter ago      |
    33. |  5 | 2019-12-12 | More than a quarter ago      |
    34. |  6 | 2020-01-05 | Within a quarter             |