sql - 在数据库中实现类似“20 个问题”的向导

Question

我希望使用存储在 Oracle 数据库中的问题树来实现一个数据驱动的向导。在不牺牲太多性能的情况下，使数据库部分灵活（即易于添加新的问题路径）的最佳模式是什么？

Answer 1

您可以使用引用同一个表的外键构建树结构（通常称为“猪耳朵”关系）。然后可以使用 CONNECT BY 语法遍历树。这是一个简单的例子：

SQL> create table qs
  2  ( q_id integer primary key
  3  , parent_q_id integer references qs
  4  , parent_q_answer varchar2(1)
  5  , q_text varchar2(100)
  6* );

Table created.

SQL> insert into qs values (1, null, null, 'Is it bigger than a person?');

1 row created.

SQL> insert into qs values (2, 1, 'Y', 'Does it have a long neck?');

1 row created.

SQL> insert into qs values (3, 2, 'Y', 'It is a giraffe');

1 row created.

SQL> insert into qs values (4, 2, 'N', 'It is an elephant');

1 row created.

SQL> insert into qs values (5, 1, 'N', 'Does it eat cheese?');

1 row created.

SQL> insert into qs values (6, 5, 'Y', 'It is a mouse');

1 row created.

SQL> insert into qs values (7, 5, 'N', 'It is a cat');

1 row created.

SQL> commit;

Commit complete.

SQL> select rpad('    ',level*4,' ')||parent_q_answer||': '||q_text
  2  from qs
  3  start with parent_q_id is null
  4  connect by prior q_id = parent_q_id;

RPAD('',LEVEL*4,'')||PARENT_Q_ANSWER||':'||Q_TEXT
------------------------------------------------------------------------------------------------------------------------------
    : Is it bigger than a person?
        Y: Does it have a long neck?
            Y: It is a giraffe
            N: It is an elephant
        N: Does it eat cheese?
            Y: It is a mouse
            N: It is a cat

7 rows selected.

请注意如何使用特殊关键字 LEVEL 来确定我们在树的下方有多远，然后我用它来缩进数据以显示结构。