oracle 层次查询判断叶子和根节点

oracle 9i判断是叶子或根节点，是比较麻烦的一件事情，SQL演示脚本如下:

DROP TABLE idb_hierarchical;  
create TABLE idb_hierarchical  
(  
id number,  
parent_id number,  
str varchar2(10)  
);  
  
insert into idb_hierarchical values(1,null,'A');  
insert into idb_hierarchical values(2,1,'B');  
insert into idb_hierarchical values(3,2,'C');  
insert into idb_hierarchical values(4,3,'D');  
insert into idb_hierarchical values(5,2,'E');  
insert into idb_hierarchical values(6,2,'F');  
insert into idb_hierarchical values(7,3,'G');  
insert into idb_hierarchical values(8,4,'H');  
insert into idb_hierarchical values(9,4,'I');  
insert into idb_hierarchical values(10,null,'J');  
insert into idb_hierarchical values(11,10,'K');  
insert into idb_hierarchical values(12,11,'L');  
insert into idb_hierarchical values(13,10,'M'); 

DROP TABLE idb_hierarchical;  
create TABLE idb_hierarchical  
(  
id number,  
parent_id number,  
str varchar2(10)  
);  
  
insert into idb_hierarchical values(1,null,'A');  
insert into idb_hierarchical values(2,1,'B');  
insert into idb_hierarchical values(3,2,'C');  
insert into idb_hierarchical values(4,3,'D');  
insert into idb_hierarchical values(5,2,'E');  
insert into idb_hierarchical values(6,2,'F');  
insert into idb_hierarchical values(7,3,'G');  
insert into idb_hierarchical values(8,4,'H');  
insert into idb_hierarchical values(9,4,'I');  
insert into idb_hierarchical values(10,null,'J');  
insert into idb_hierarchical values(11,10,'K');  
insert into idb_hierarchical values(12,11,'L');  

insert into idb_hierarchical values(13,10,'M'); 
示例数据清单如下:

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL  
  FROM idb_hierarchical  
 START WITH PARENT_ID IS NULL  
CONNECT BY PARENT_ID = PRIOR ID;  

表1:数据清单
STR_LEVEL ID PARENT_ID LVL
+..A 1 1
+….B 2 1 2
+……C 3 2 3
+……..D 4 3 4
+……….H 8 4 5
+……….I 9 4 5
+……..G 7 3 4
+……E 5 2 3
+……F 6 2 3
+..J 10 1
+….K 11 10 2
+……L 12 11 3
+….M 13 10 2
在表1中，ID为8、9、 7、5、6、12、13都没有子节点，因此称为叶节点。

1.oracle9i 查询叶节点
只显示叶子节点SQL

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL  
  FROM idb_hierarchical I  
  --在oracle 9i中显示叶节点，需要判断是否有子节点即可  
  WHERE NOT EXISTS(SELECT 1  
  FROM idb_hierarchical B  
  WHERE I.ID=B.PARENT_ID)  
 START WITH PARENT_ID IS NULL  
CONNECT BY PARENT_ID = PRIOR ID;  

表2
STR_LEVEL ID PARENT_ID LVL
+……….H 8 4 5
+……….I 9 4 5
+……..G 7 3 4
+……E 5 2 3
+……F 6 2 3
+……L 12 11 3
+….M 13 10 2
显示所有节点，标明该行是否为叶节点SQL

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL,  
NVL((SELECT 'N'  
  FROM idb_hierarchical B  
  WHERE I.ID=B.PARENT_ID  
  AND ROWNUM  < 2),'Y') IS_LEAF  
  FROM idb_hierarchical I  
 START WITH PARENT_ID IS NULL  
CONNECT BY PARENT_ID = PRIOR ID;  

表3
STR_LEVEL ID PARENT_ID LVL IS_LEAF
+..A 1 1 N
+....B 2 1 2 N
+......C 3 2 3 N
+........D 4 3 4 N
+..........H 8 4 5 Y
+..........I 9 4 5 Y
+........G 7 3 4 Y
+......E 5 2 3 Y
+......F 6 2 3 Y
+..J 10 1 N
+....K 11 10 2 N
+......L 12 11 3 Y
+....M 13 10 2 Y

oracle 9i 查询根节点

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL  
  FROM idb_hierarchical I  
 START WITH id =2  
CONNECT BY PARENT_ID = PRIOR ID; 

表4
STR_LEVEL ID PARENT_ID LVL
+..B 2 1 1
+....C 3 2 2
+......D 4 3 3
+........H 8 4 4
+........I 9 4 4
+......G 7 3 3
+....E 5 2 2
+....F 6 2 2
根节点ID应该为3、5、6，即lvl为1即可

查询根节点，只显示根节点SQL

SELECT RPAD('+', LEVEL * 2 + 1, '.') || STR STR_LEVEL,  
       ID,  
       PARENT_ID,  
       LEVEL LVL,  
       (select b.str  
          from idb_hierarchical b  
         where level = 1  
         start with b.id = 2  
        connect by prior b.id =  b.parent_id  
        ) root_str  
  FROM idb_hierarchical I  
 where level = 1  
 START WITH id = 2  
CONNECT BY PARENT_ID = PRIOR ID;  

表5
STR_LEVEL ID PARENT_ID LVL ROOT_STR
+..B 2 1 1 B
标明根节点SQL

SELECT RPAD('+', LEVEL * 2 + 1, '.') || STR STR_LEVEL,  
       ID,  
       PARENT_ID,  
       DECODE(LEVEL, 1, 'Y', 'N') is_root,  
       LEVEL LVL,  
       (select b.str  
          from idb_hierarchical b  
         where level = 1  
         start with b.id = 2  
        connect by prior b.id = b.parent_id) root_str  
  FROM idb_hierarchical I  
 START WITH id = 2  
CONNECT BY PARENT_ID = PRIOR ID;  

表6
STR_LEVEL ID PARENT_ID IS_ROOT LVL ROOT_STR
+..B 2 1 Y 1 B
+....C 3 2 N 2 B
+......D 4 3 N 3 B
+........H 8 4 N 4 B
+........I 9 4 N 4 B
+......G 7 3 N 3 B
+....E 5 2 N 2 B
+....F 6 2 N 2 B
在oracle 10g提供了connect_by_isleaf和connect_by_root

oracle 10g用connect_by_isleaf判断叶节点

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL  
  FROM idb_hierarchical I  
where connect_by_isleaf=1  
 START WITH PARENT_ID IS NULL  
CONNECT BY PARENT_ID = PRIOR ID;  

表7
STR_LEVEL ID PARENT_ID LVL
+..........H 8 4 5
+..........I 9 4 5
+........G 7 3 4
+......E 5 2 3
+......F 6 2 3
+......L 12 11 3
+....M 13 10 2

SELECT RPAD('+',LEVEL*2+1,'.')||STR STR_LEVEL,ID,PARENT_ID,LEVEL LVL,  
decode(connect_by_isleaf,1,'Y','N') IS_LEAF  
  FROM idb_hierarchical I  
 START WITH PARENT_ID IS NULL  
CONNECT BY PARENT_ID = PRIOR ID;  

表8
STR_LEVEL ID PARENT_ID LVL IS_LEAF
+..A 1 1 N
+....B 2 1 2 N
+......C 3 2 3 N
+........D 4 3 4 N
+..........H 8 4 5 Y
+..........I 9 4 5 Y
+........G 7 3 4 Y
+......E 5 2 3 Y
+......F 6 2 3 Y
+..J 10 1 N
+....K 11 10 2 N
+......L 12 11 3 Y
+....M 13 10 2 Y
oracle 10g用connect_by_root判断根节点

SELECT RPAD('+', LEVEL * 2 + 1, '.') || STR STR_LEVEL,  
       ID,  
       PARENT_ID,  
       LEVEL LVL,  
       connect_by_root STR ROOT_STR  
  FROM idb_hierarchical I  
 START WITH id = 2  
CONNECT BY PARENT_ID = PRIOR ID;  

表9
STR_LEVEL ID PARENT_ID LVL ROOT_STR
+..B 2 1 1 B
+....C 3 2 2 B
+......D 4 3 3 B
+........H 8 4 4 B
+........I 9 4 4 B
+......G 7 3 3 B
+....E 5 2 2 B
+....F 6 2 2 B

SELECT RPAD('+', LEVEL * 2 + 1, '.') || STR STR_LEVEL,  
       ID,  
       PARENT_ID,  
       DECODE(LEVEL, 1, 'Y', 'N') is_root,  
       LEVEL LVL,  
       connect_by_root STR ROOT_STR  
  FROM idb_hierarchical I  
 START WITH id = 3  
CONNECT BY PARENT_ID = PRIOR ID;  

表10
STR_LEVEL ID PARENT_ID IS_ROOT LVL ROOT_STR
+..C 3 2 Y 1 C
+....D 4 3 N 2 C
+......H 8 4 N 3 C
+......I 9 4 N 3 C
+....G 7 3 N 2 C

SELECT RPAD('+', LEVEL * 2 + 1, '.') || STR STR_LEVEL,  
       ID,  
       PARENT_ID,  
       DECODE(LEVEL, 1, 'Y', 'N') is_root,  
       LEVEL LVL,  
       connect_by_root STR ROOT_STR  
  FROM idb_hierarchical I  
 START WITH PARENT_ID = 2  
CONNECT BY PARENT_ID = PRIOR ID;  

表11
STR_LEVEL ID PARENT_ID IS_ROOT LVL ROOT_STR
+..C 3 2 Y 1 C
+....D 4 3 N 2 C
+......H 8 4 N 3 C
+......I 9 4 N 3 C
+....G 7 3 N 2 C
+..E 5 2 Y 1 E
+..F 6 2 Y 1 F