【问题标题】：SQL Challenge/Puzzle: How to create an ASCII art hierarchy tree with an SQL query?SQL Challenge/Puzzle：如何使用 SQL 查询创建 ASCII 艺术层次结构树？
【发布时间】：2016-10-07 21:17:57
【问题描述】：

制作这个的最初动机是，以直观、清晰的方式显示 Oracle 的实际执行计划，保存在 GV$SQL_PLAN 中。

我附上了我建议的解决方案。
- 只要满足要求，请随时添加您的。
- 请提及您的解决方案所针对的数据库名称。

要求

输入

包含列“id”（节点的 ID）和“pid”（节点的父 ID）的表。

输出

结果应该是一个 ASCII 艺术图（见下面的例子）
- 每对“id”和“pid”节点都应与一条边相连。
- 根节点可能有一个额外的单边。
- 不应有其他边，尤其是未连接到其一侧的任何节点的边。

代码

仅基于本机 SQL 的单个 SELECT 语句
- 没有 UDF（用户定义函数）。
- 没有 T-SQL、PL/SQL 等

样本数据

create table h (id int,pid int);

insert into h (id,pid) values (0  ,null);
insert into h (id,pid) values (1  ,0   );
insert into h (id,pid) values (2  ,1   );
insert into h (id,pid) values (3  ,2   );
insert into h (id,pid) values (4  ,3   );
insert into h (id,pid) values (5  ,4   );
insert into h (id,pid) values (6  ,3   );
insert into h (id,pid) values (7  ,6   );
insert into h (id,pid) values (8  ,7   );
insert into h (id,pid) values (9  ,8   );
insert into h (id,pid) values (10 ,9   );
insert into h (id,pid) values (11 ,10  );
insert into h (id,pid) values (12 ,9   );
insert into h (id,pid) values (13 ,12  );
insert into h (id,pid) values (14 ,8   );
insert into h (id,pid) values (15 ,6   );
insert into h (id,pid) values (16 ,15  );
insert into h (id,pid) values (17 ,6   );
insert into h (id,pid) values (18 ,17  );
insert into h (id,pid) values (19 ,17  );
insert into h (id,pid) values (20 ,3   );
insert into h (id,pid) values (21 ,20  );
insert into h (id,pid) values (22 ,21  );
insert into h (id,pid) values (23 ,22  );
insert into h (id,pid) values (24 ,21  );

结果

垂直同级

|
|____ 1
     |
     |____ 2
          |
          |____ 3
               |
               |____ 4
               |    |
               |    |____ 5
               |
               |____ 6
               |    |
               |    |____ 7
               |    |    |
               |    |    |____ 8
               |    |         |
               |    |         |____ 9
               |    |         |    |
               |    |         |    |____ 10
               |    |         |    |    |
               |    |         |    |    |____ 11
               |    |         |    |
               |    |         |    |____ 12
               |    |         |         |
               |    |         |         |____ 13
               |    |         |
               |    |         |____ 14
               |    |
               |    |____ 15
               |    |    |
               |    |    |____ 16
               |    |
               |    |____ 17
               |         |
               |         |____ 18
               |         |
               |         |____ 19
               |
               |____ 20
                    |
                    |____ 21
                         |
                         |____ 22
                         |    |
                         |    |____ 23
                         |
                         |____ 24

水平的兄弟姐妹

                      |                      
                      |                      
                      |                      
                      0                      
                      |                      
                      |                      
                      |                      
                      |                      
                      |                      
                      1                      
                      |                      
                      |                      
                      |                      
                      |                      
                      |                      
                      2                      
                      |                      
                      |                      
                      |                      
                      |                      
                      |                      
                      3                      
                      |                      
                      |                      
  ---------------------------------------    
  |                 |                   |    
  |                 |                   |    
  4                 6                   20   
  |                 |                   |    
  |                 |                   |    
  |         -------------------         |    
  |         |         |       |         |    
  |         |         |       |         |    
  5         7         15      17        21   
            |         |       |         |    
            |         |       |         |    
            |         |    ------    ------  
            |         |    |    |    |    |  
            |         |    |    |    |    |  
            8         16   18   19   22   24 
            |                        |       
            |                        |       
          --------                   |  
          |      |                   |  
          |      |                   |  
          9      14                  23 
          |                             
          |                             
       ------  
       |    |  
       |    |  
       10   12 
       |    |  
       |    |  
       |    |  
       |    |  
       |    |  
       11   13

【问题讨论】：

标签： sql graph tree hierarchy ascii-art

【解决方案1】：

甲骨文

垂直同级

with        last_sibling (id)
            as
            (
                select      max (id)
                from        h
                group by    pid
            )

           ,tree (id,pid,branch) as
            (
                 select     h.id
                           ,h.pid
                           ,cast ('' as varchar (4000))

                 from       h

                 where      h.pid is null

                 union all

                 select     h.id
                           ,h.pid
                           ,t.branch || case when ls.id is not null then ' ' else '|' end || '    '

                 from                   tree            t

                            left join   last_sibling    ls

                            on          ls.id   =
                                        t.id

                            join        h

                            on          h.pid =
                                        t.id

                    ) search depth first by id set order_by_id

           ,vertical_space (n)
            as
            (
                select      1
                from        dual

                union all

                select      vs.n + 1
                from        vertical_space  vs
                where       vs.n - 1 < 1
            )

select      t.branch || case vs.n when 1 then '|____' || ' ' || cast (t.id as varchar(10)) else '|' end

from                    tree            t

            cross join  vertical_space  vs

order by    t.order_by_id
           ,vs.n desc
;

【讨论】：

【解决方案2】：

甲骨文

水平的兄弟姐妹

with        il_parameters (atomic_width) as
            (
                 select     5   
            
                 from       dual
            )
            
select      decode
            (
                 n.n      
               
                ,1
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (decode (h.n_within_parent,1,decode (h.n_desc_within_parent,1,'|','-'),'-'),h.width/2 * il_parameters.atomic_width + 1,decode (h.n_within_parent,1,' ','-')),h.width * il_parameters.atomic_width,decode (h.n_desc_within_parent,1,' ','-'))
                 ) within group (order by h.id)                               
                                                       
                ,2
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (' ',h.width/2 * il_parameters.atomic_width,' ') || '|' ,h.width * il_parameters.atomic_width)
                 ) within group (order by h.id)                        
                
                ,3
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (' ',h.width/2 * il_parameters.atomic_width,' ') || '|' ,h.width * il_parameters.atomic_width)
                 ) within group (order by h.id)    
                                         
                ,4
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (' ',h.width/2 * il_parameters.atomic_width,' ') || h.id,h.width * il_parameters.atomic_width)
                 ) within group (order by h.id)     
                 
                ,5
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (' ',h.width/2 * il_parameters.atomic_width,' ') || decode (h.isleaf,0,'|',' ') ,h.width * il_parameters.atomic_width)
                 ) within group (order by h.id)   
                       
                ,6
                
                ,listagg 
                 (
                      lpad (' ',x_lpad * il_parameters.atomic_width) 
                   || rpad (lpad (' ',h.width/2 * il_parameters.atomic_width,' ') || decode (h.isleaf,0,'|',' ') ,h.width * il_parameters.atomic_width)
                 ) within group (order by h.id)                                                                     
            )                                                           graph
            
            

from                       (select          h.id                                                                                 id
                                           ,h.width                                                                              width
                                           ,h.y                                                                                  y
                                           ,h.isleaf                                                                             isleaf
                                           ,h.n_within_parent                                                                    n_within_parent
                                           ,h.n_desc_within_parent                                                               n_desc_within_parent                                                                       
                                           
                                           ,     sum (regexp_substr (heirarchy_x_within_parent,'\d+',1,n.n))
                                               - lag (sum (regexp_substr (heirarchy_x_within_parent,'\d+',1,n.n)),1,0) over
                                                 (
                                                      partition by   h.y
                                                                    
                                                      order by       h.id
                                                 ) 
                                               - lag (h.width,1,0) over
                                                 (
                                                      partition by   h.y
                                                                    
                                                      order by       h.id
                                                 )                                                                               x_lpad
                                               
                                            
                                            
                            from                           (select      h.id
                                                                       ,h.width
                                                                       ,h.n_within_parent
                                                                       ,h.n_desc_within_parent
                                                                       ,level                                        y
                                                                       ,sys_connect_by_path (x_within_parent,',')    heirarchy_x_within_parent
                                                                       ,connect_by_isleaf                            isleaf                          
                                                                             
                                                            from       (select      h.id                                              id
                                                                                   ,h.pid                                             pid
                                                                                   ,count (*)                                         width
                                                                                                            
                                                                                   ,nvl
                                                                                    (
                                                                                         sum (count (*)) over
                                                                                         (
                                                                                              partition by   h.pid
                                                                                                            
                                                                                              order by       h.id
                                                                                              
                                                                                              rows between   unbounded preceding
                                                                                                   and       1 preceding 
                                                                                         )
                                                                                        ,0
                                                                                    )                                                 x_within_parent
                                                                                    
                                                                                   ,row_number () over
                                                                                    (
                                                                                         partition by   h.pid
                                                                                                       
                                                                                         order by       h.id
                                                                                    )                                                 n_within_parent
                                                                                    
                                                                                   ,row_number () over
                                                                                    (
                                                                                         partition by   h.pid
                                                                                                       
                                                                                         order by       h.id desc
                                                                                    )                                                 n_desc_within_parent
                                                          
                                                                        from       (select      connect_by_root h.id          id  
                                                                                               ,connect_by_root h.pid         pid                                                       
                                                                                                
                                                                                    from        h
                                                                                                
                                                                                    where       connect_by_isleaf = 1
                                                                                                
                                                                                    connect by  h.pid = prior h.id
                                                                                    ) h
                                                          
                                                                        group by    h.id 
                                                                                   ,h.pid
                                                                        ) h
                                                                                            
                                                            connect by  h.pid = prior h.id
                                                                                 
                                                            start with  h.pid is null 
                                                            ) h
                                                            
                                            join           (select      rownum n 
                                                            from        dual 
                                                            connect by  level <= 100
                                                           ) n
                                                           
                                            on              n.n <=
                                                            regexp_count (h.heirarchy_x_within_parent,',') 
                                                           
                            group by        h.id  
                                           ,h.width       
                                           ,h.y 
                                           ,h.isleaf
                                           ,h.n_within_parent                                                                    
                                           ,h.n_desc_within_parent                                                                          
                            ) h     
            
            cross join      il_parameters
                                
            cross join     (select      rownum n 
                            from        dual 
                            connect by  level <= 6
                           )  n
            
group by    h.y  
           ,n.n

order by    h.y 
           ,n.n                                                                                                                                       
;

【讨论】：

【解决方案3】：

SQLite

垂直同级

with        last_sibling (id)
            as
            (
                select      max (id)
                from        h
                group by    pid
            )

           ,tree (id,branch,path)
            as
            (
                select      1       as id
                           ,''      as branch
                           ,'001'   as path

                union all

                select      h.id
                           ,t.branch || case when ls.id is not null then ' ' else '|' end || '    '
                           ,t.path || '_' || substr ('00000' || h.id,-5)

                from                    tree            t

                            left join   last_sibling    ls

                            on          ls.id   =
                                        t.id

                            join        h

                            on          h.pid =
                                        t.id
            )

           ,vertical_space (n)
            as
            (
                select      1

                union all

                select      vs.n + 1
                from        vertical_space  vs
                where       vs.n < 2
            )

select      t.branch || case vs.n when 1 then '|____' || ' ' || cast (t.id as text) else '|' end

from                    tree            t

            cross join  vertical_space  vs

order by    t.path
           ,vs.n desc
;

【讨论】：

【解决方案4】：

SQL 服务器

垂直同级

with        last_sibling (id)
            as
            (
                select      max (id)
                from        h
                group by    pid
            )

           ,tree (id,branch,path)
            as
            (
                select      h.id
                           ,cast ('' as varchar(max))
                           ,cast (right (replicate ('0',10) + cast (h.id as varchar(10)),10) as varchar(max))

                from        h

                where       h.pid is null

                union all

                select      h.id
                           ,t.branch + case when (select 1 xxxfrom last_sibling ls where ls.id = t.id) = 1 then ' ' else '|' end + '    '
                           ,t.path + '_' + right (replicate ('0',10) + cast (h.id as varchar(10)),10)

                from                    tree            t

                            join        h

                            on          h.pid =
                                        t.id
            )

           ,vertical_space (n)
            as
            (
                select      1

                union all

                select      vs.n + 1
                from        vertical_space  vs
                where       vs.n < 2
            )

select      t.branch + case vs.n when 1 then '|____' + ' ' + cast (t.id as varchar(10)) else '|' end

from                    tree            t

            cross join  vertical_space  vs

order by    t.path
           ,vs.n desc

option      (maxrecursion 0)
;

【讨论】：

由于某种原因，stackoverflow 代码编辑器不喜欢子查询中的“来自”这个词。请将 'xxxfrom' 替换为 'from'

【解决方案5】：

Teradata

垂直同级

with        recursive tree (id,branch,path)
            as
            (
                select      1                               as id
                           ,cast (''    as varchar (1000))  as branch
                           ,cast ('001' as varchar (1000))  as path
                           
                from        (select 'x') x(x)

                union all

                select      h.id
                           ,t.branch || case when ls.id is not null then ' ' else '|' end || '    '
                           ,t.path || '_' || substr ('00000' || h.id,-5)

                from                    tree            t

                            left join   last_sibling    ls

                            on          ls.id   =
                                        t.id

                            join        h

                            on          h.pid =
                                        t.id
            )

           ,last_sibling (id)
            as
            (
                select      max (id)
                from        h
                group by    pid
            )

           ,recursive vertical_space (n)
            as
            (
                select      1
                
                from        (select 'x') x(x)

                union all

                select      vs.n + 1
                from        vertical_space  vs
                where       vs.n < 2
            )

select      t.branch || case vs.n when 1 then '|____' || ' ' || cast (t.id as varchar(10)) else '|' end

from                    tree            t

            cross join  vertical_space  vs

order by    t.path
           ,vs.n desc
;

【讨论】：