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MYSQL教程mysql遞歸查詢實現(xiàn)方法

作者：VEPHP   時間 2017-09-27

《MYSQL教程mysql遞歸查詢實現(xiàn)方法》要點：
本文介紹了MYSQL教程mysql遞歸查詢實現(xiàn)方法，希望對您有用。如果有疑問，可以聯(lián)系我們。

導讀：在Oracle 中有一個 Hierarchical Queries 通過CONNECT BY 可以方便的查了所有當前節(jié)點下的所有子節(jié)點.在MySQL的目前版本中還沒有對...

MYSQL應(yīng)用在Oracle 中有一個 Hierarchical Queries 通過CONNECT BY 可以方便的查了所有當前節(jié)點下的所有子節(jié)點.
在MySQL的目前版本中還沒有對應(yīng)的功能.
?
在MySQL中如果是有限的層次,比如事先如果可以確定這個樹的最大深度是4, 那么所有節(jié)點為根的樹的深度均不會超過4,則可以直接通過left join 來實現(xiàn).
?
但有時無法控制樹的深度.這時就需要在MySQL中用存儲過程來實現(xiàn)或在你的程序中來實現(xiàn)這個遞歸.

MYSQL應(yīng)用本文討論一下幾種實現(xiàn)的辦法.
?
樣例數(shù)據(jù)：
?

mysql> create table treeNodes
??? -> (
??? ->? id int primary key,
??? ->? nodename varchar(20),
??? ->? pid int
??? -> );
Query OK, 0 rows affected (0.09 sec)
mysql> select * from treenodes;
+----+----------+------+
| id | nodename | pid? |
+----+----------+------+
|? 1 | A??????? |??? 0 |
|? 2 | B??????? |??? 1 |
|? 3 | C??????? |??? 1 |
|? 4 | D??????? |??? 2 |
|? 5 | E??????? |??? 2 |
|? 6 | F??????? |??? 3 |
|? 7 | G??????? |??? 6 |
|? 8 | H??????? |??? 0 |
|? 9 | I??????? |??? 8 |
| 10 | J??????? |??? 8 |
| 11 | K??????? |??? 8 |
| 12 | L??????? |??? 9 |
| 13 | M??????? |??? 9 |
| 14 | N??????? |?? 12 |
| 15 | O??????? |?? 12 |
| 16 | P??????? |?? 15 |
| 17 | Q??????? |?? 15 |
+----+----------+------+
17 rows in set (0.00 sec)
?

MYSQL應(yīng)用樹形圖：
?

1:A
? +-- 2:B
? |??? +-- 4:D
? |??? +-- 5:E
? +-- 3:C
?????? +-- 6:F
??????????? +-- 7:G
?8:H
? +-- 9:I
? |??? +-- 12:L
? |??? |??? +--14:N
? |??? |??? +--15:O
? |??? |??????? +--16:P
? |??? |??????? +--17:Q
? |??? +-- 13:M
? +-- 10:J
? +-- 11:K?
?

MYSQL應(yīng)用?
辦法一：利用函數(shù)來得到所有子節(jié)點號.
創(chuàng)建一個function getChildLst, 得到一個由所有子節(jié)點號組成的字符串.
?

MYSQL應(yīng)用mysql> delimiter //
mysql>
mysql> CREATE FUNCTION `getChildLst`(rootId INT)
??? -> RETURNS varchar(1000)
??? -> BEGIN
??? ->?? DECLARE sTemp VARCHAR(1000);
??? ->?? DECLARE sTempChd VARCHAR(1000);
??? ->
??? ->?? SET sTemp = '$';
??? ->?? SET sTempChd =cast(rootId as CHAR);
??? ->
??? ->?? WHILE sTempChd is not null DO
??? ->???? SET sTemp = concat(sTemp,',',sTempChd);
??? ->???? SELECT group_concat(id) INTO sTempChd FROM treeNodes where FIND_IN_SET(pid,sTempChd)>0;
??? ->?? END WHILE;
??? ->?? RETURN sTemp;
??? -> END
??? -> //
Query OK, 0 rows affected (0.00 sec)

MYSQL應(yīng)用mysql>
mysql> delimiter ;

MYSQL應(yīng)用使用直接利用find_in_set函數(shù)配合這個getChildlst來查找：
?

MYSQL應(yīng)用mysql> select getChildLst(1);
+-----------------+
| getChildLst(1)? |
+-----------------+
| $,1,2,3,4,5,6,7 |
+-----------------+
1 row in set (0.00 sec)

MYSQL應(yīng)用mysql> select * from treeNodes
??? -> where FIND_IN_SET(id, getChildLst(1));
+----+----------+------+
| id | nodename | pid? |
+----+----------+------+
|? 1 | A??????? |??? 0 |
|? 2 | B??????? |??? 1 |
|? 3 | C??????? |??? 1 |
|? 4 | D??????? |??? 2 |
|? 5 | E??????? |??? 2 |
|? 6 | F??????? |??? 3 |
|? 7 | G??????? |??? 6 |
+----+----------+------+
7 rows in set (0.01 sec)

MYSQL應(yīng)用mysql> select * from treeNodes
??? -> where FIND_IN_SET(id, getChildLst(3));
+----+----------+------+
| id | nodename | pid? |
+----+----------+------+
|? 3 | C??????? |??? 1 |
|? 6 | F??????? |??? 3 |
|? 7 | G??????? |??? 6 |
+----+----------+------+
3 rows in set (0.01 sec)
?
?

MYSQL應(yīng)用優(yōu)點: 簡單,方便,沒有遞歸調(diào)用層次深度的限制 (max_sp_recursion_depth,最大255) ；
缺點：長度受限,雖然可以擴大 RETURNS varchar(1000),但總是有最大限制的.
MySQL目前版本( 5.1.33-community)中還不支持function 的遞歸調(diào)用.
?
辦法二：利用臨時表和過程遞歸
創(chuàng)建存儲過程如下.createChildLst 為遞歸過程,showChildLst為調(diào)用入口過程,準備臨時表及初始化.
?

MYSQL應(yīng)用mysql> delimiter //
mysql>
mysql> # 入口過程
mysql> CREATE PROCEDURE showChildLst (IN rootId INT)
??? -> BEGIN
??? ->? CREATE TEMPORARY TABLE IF NOT EXISTS tmpLst
??? ->?? (sno int primary key auto_increment,id int,depth int);
??? ->? DELETE FROM tmpLst;
??? ->
??? ->? CALL createChildLst(rootId,0);
??? ->
??? ->? select tmpLst.*,treeNodes.* from tmpLst,treeNodes where tmpLst.id=treeNodes.id order by tmpLst.sno;
??? -> END;
??? -> //
Query OK, 0 rows affected (0.00 sec)

MYSQL應(yīng)用mysql>
mysql> # 遞歸過程
mysql> CREATE PROCEDURE createChildLst (IN rootId INT,IN nDepth INT)
??? -> BEGIN
??? ->? DECLARE done INT DEFAULT 0;
??? ->? DECLARE b INT;
??? ->? DECLARE cur1 CURSOR FOR SELECT id FROM treeNodes where pid=rootId;
??? ->? DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
??? ->
??? ->? insert into tmpLst values (null,rootId,nDepth);
??? ->
??? ->? OPEN cur1;
??? ->
??? ->? FETCH cur1 INTO b;
??? ->? WHILE done=0 DO
??? ->????????? CALL createChildLst(b,nDepth+1);
??? ->????????? FETCH cur1 INTO b;
??? ->? END WHILE;
??? ->
??? ->? CLOSE cur1;
??? -> END;
??? -> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;

MYSQL應(yīng)用調(diào)用時傳入結(jié)點：
?

MYSQL應(yīng)用mysql> call showChildLst(1);
+-----+------+-------+----+----------+------+
| sno | id?? | depth | id | nodename | pid? |
+-----+------+-------+----+----------+------+
|?? 4 |??? 1 |???? 0 |? 1 | A??????? |??? 0 |
|?? 5 |??? 2 |???? 1 |? 2 | B??????? |??? 1 |
|?? 6 |??? 4 |???? 2 |? 4 | D??????? |??? 2 |
|?? 7 |??? 5 |???? 2 |? 5 | E??????? |??? 2 |
|?? 8 |??? 3 |???? 1 |? 3 | C??????? |??? 1 |
|?? 9 |??? 6 |???? 2 |? 6 | F??????? |??? 3 |
|? 10 |??? 7 |???? 3 |? 7 | G??????? |??? 6 |
+-----+------+-------+----+----------+------+
7 rows in set (0.13 sec)

MYSQL應(yīng)用Query OK, 0 rows affected, 1 warning (0.14 sec)

MYSQL應(yīng)用mysql>
mysql> call showChildLst(3);
+-----+------+-------+----+----------+------+
| sno | id?? | depth | id | nodename | pid? |
+-----+------+-------+----+----------+------+
|?? 1 |??? 3 |???? 0 |? 3 | C??????? |??? 1 |
|?? 2 |??? 6 |???? 1 |? 6 | F??????? |??? 3 |
|?? 3 |??? 7 |???? 2 |? 7 | G??????? |??? 6 |
+-----+------+-------+----+----------+------+
3 rows in set (0.11 sec)

MYSQL應(yīng)用Query OK, 0 rows affected, 1 warning (0.11 sec)
?

MYSQL應(yīng)用depth 為深度,這樣可以在程序進行一些顯示上的格式化處理.類似于oracle中的 level 偽列.sno 僅供排序控制.
這樣還可以通過臨時表tmpLst與數(shù)據(jù)庫中其它表進行聯(lián)接查詢.
?
MySQL中可以利用系統(tǒng)參數(shù) max_sp_recursion_depth 來控制遞歸調(diào)用的層數(shù)上限.如下例設(shè)為12.
?

mysql> set max_sp_recursion_depth=12;
Query OK, 0 rows affected (0.00 sec)
?

MYSQL應(yīng)用?
優(yōu)點 : 可以更靈活處理,及層數(shù)的顯示.并且可以依照樹的遍歷順序得到結(jié)果.
缺點 : 遞歸有255的限制.
?
方法三：利用中間表和過程
(本方法由yongyupost2000提供樣子改編)
創(chuàng)建存儲過程如下.
由于MySQL中不允許在同一語句中對臨時表多次引用,只以使用普通表tmpLst來實現(xiàn)了.
當然程序中負責在用完后清除這個表.
?

delimiter //
drop PROCEDURE IF EXISTS? showTreeNodes_yongyupost2000//
CREATE PROCEDURE showTreeNodes_yongyupost2000 (IN rootid INT)
BEGIN
?DECLARE Level int ;
?drop TABLE IF EXISTS tmpLst;
?CREATE TABLE tmpLst (
? id int,
? nLevel int,
? sCort varchar(8000)
?);
?
?Set Level=0 ;
?INSERT into tmpLst SELECT id,Level,ID FROM treeNodes WHERE PID=rootid;
?WHILE ROW_COUNT()>0 DO
? SET Level=Level+1 ;
? INSERT into tmpLst
?? SELECT A.ID,Level,concat(B.sCort,A.ID) FROM treeNodes A,tmpLst B
??? WHERE? A.PID=B.ID AND B.nLevel=Level-1? ;
?END WHILE;
?
END;
//
delimiter ;
CALL showTreeNodes_yongyupost2000(0);
?

MYSQL應(yīng)用執(zhí)行完后會產(chǎn)生一個tmpLst表,nLevel 為節(jié)點深度,sCort 為排序字段.
使用辦法：
?

SELECT concat(SPACE(B.nLevel*2),'+--',A.nodename)
FROM treeNodes A,tmpLst B
WHERE A.ID=B.ID
ORDER BY B.sCort;
?
+--------------------------------------------+
| concat(SPACE(B.nLevel*2),'+--',A.nodename) |
+--------------------------------------------+
| +--A?????????????????????????????????????? |
|?? +--B???????????????????????????????????? |
|???? +--D?????????????????????????????????? |
|???? +--E?????????????????????????????????? |
|?? +--C???????????????????????????????????? |
|???? +--F?????????????????????????????????? |
|?????? +--G???????????????????????????????? |
| +--H?????????????????????????????????????? |
|?? +--J???????????????????????????????????? |
|?? +--K???????????????????????????????????? |
|?? +--I???????????????????????????????????? |
|???? +--L?????????????????????????????????? |
|?????? +--N???????????????????????????????? |
|?????? +--O???????????????????????????????? |
|???????? +--P?????????????????????????????? |
|???????? +--Q?????????????????????????????? |
|???? +--M?????????????????????????????????? |
+--------------------------------------------+
17 rows in set (0.00 sec)

MYSQL應(yīng)用以上介紹了mysql遞歸查詢的實現(xiàn)辦法與實例代碼,希望對大家有所幫助.

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