表依赖项的递归查询没有像我希望的那样递归

你想要这样的东西:

select t.table_name, level,lpad(' ', 2 * (level - 1))||t.table_name 
from user_tables t
join user_constraints c1 
    on (t.table_name = c1.table_name 
    and c1.constraint_type in ('U', 'P'))
left join user_constraints c2 
    on (t.table_name = c2.table_name 
    and c2.constraint_type='R')
start with t.table_name = 'ROOT_TAB'
connect by prior c1.constraint_name = c2.r_constraint_name

原始查询的问题是子表的uc.constraint_name是外键的名称。这对于将第一个子级连接到根表来说是很好的,但是您不需要将第二级的子级连接到第一级。这就是为什么您需要针对约束进行两次联接——一次是获取表的主键,一次是获取外键。

顺便说一句,如果您要查询所有的视图而不是用户的视图,那么您通常希望将它们加入到表名和所有者中,而不仅仅是表名。如果多个架构具有相同名称的表,则仅在表名上联接将产生不正确的结果。

对于具有多个模式和多个根表的情况,请尝试如下操作:

WITH constraining_tables AS (SELECT owner, constraint_name, table_name
                               FROM all_constraints
                              WHERE owner LIKE 'ZZZ%' AND constraint_type IN ('U', 'P')),
     constrained_tables AS (SELECT owner, constraint_name, table_name, r_owner, r_constraint_name
                              FROM all_constraints
                             WHERE owner LIKE 'ZZZ%' AND constraint_type = 'R'),
     root_tables AS (SELECT owner, table_name FROM constraining_tables
                     MINUS
                     SELECT owner, table_name FROM constrained_tables)
    SELECT c1.owner || '.' || c1.table_name, LEVEL, LPAD (' ', 2 * (LEVEL - 1)) || c1.owner || '.' || c1.table_name
      FROM    constraining_tables c1
           LEFT JOIN
              constrained_tables c2
           ON c1.owner = c2.owner AND c1.table_name = c2.table_name
START WITH c1.owner || '.' || c1.table_name IN (SELECT owner || '.' || table_name FROM root_tables)
CONNECT BY PRIOR c1.constraint_name = c2.r_constraint_name

经过深入调查,我制作了自己的版本,它处理所有表,并检索表在层次结构中的最大级别(它读取所有模式,同时考虑到没有父子关系的表,这些表将与根表一起位于级别1)。如果您有访问权限,请使用DBA表格而不是所有表格。

      WITH hier AS (
                         SELECT child_table owner_table_name
                              , LEVEL lvl
                              , LPAD (' ', 4 * (LEVEL - 1)) || child_table indented_child_table
                              , sys_connect_by_path( child_table, '|' )  tree
                           FROM (
/*----------------------------------------------------------------------*/
/* Retrieve all tables. Set them as the Child column, and set their     */
/* Parent Column to NULL. This is the root list (first iteration)       */
/*----------------------------------------------------------------------*/
                                  SELECT NULL                              parent_table
                                       , a.owner || '.' || a.table_name    child_table
                                    FROM all_tables a
                                   UNION
/*----------------------------------------------------------------------*/
/* List of all possible Parent-Child relations. This table is used as   */
/* a link list, to link the current iteration with the next one, from   */
/* root to last child (last child is what we are interested to find).   */
/*----------------------------------------------------------------------*/
                                  SELECT p.owner   || '.' || p.table_name            parent_table
                                       , c.owner   || '.' || c.table_name            child_table
                                    FROM all_constraints p, all_constraints c
                                   WHERE p.owner || '.' || p.constraint_name = c.r_owner || '.' || c.r_constraint_name
                                     AND (p.constraint_type = 'P' OR p.constraint_type = 'U')
                                     AND c.constraint_type = 'R'
                                )
                     START WITH parent_table IS NULL
/*----------------------------------------------------------------------*/
/* NOCYCLE prevents infinite loops (i.e. self referencing table constr) */
/*----------------------------------------------------------------------*/
                     CONNECT BY NOCYCLE PRIOR child_table = parent_table
                   )
                     SELECT *
                       FROM hier
                      WHERE (owner_table_name, lvl) IN (   SELECT owner_table_name
                                                                , MAX(lvl)
                                                             FROM hier
                                                         GROUP BY owner_table_name
                                                       );

编辑: 在查找无限循环时,此查询存在“某种”问题。

如果我们有这棵树:

b --> c --> d
b <-- c

它将把2级分配给C级: b --> c 2级至B级: c --> b

对于D,它将检测 b --> c --> d 所以它将分配3级

因此,正如您所看到的,问题在循环内部,来自外部的值总是有其最大正确的lvl