Two methods of implementing the tree-like structure
1. Recursive method
Recursion refers to an explicit invocation of itself in a function.
The feature of the tree structure by recursion is that it is faster to write data and slower to display (especially in the case of branches/levels of trees). Applies to the case that the data volume is large and the structure of the tree is complex.
Data structure (take MySQL as an example)
Code:--------------------------------------------------------------------------------
CREATE TABLE ' Tree1 ' (
' ID ' tinyint (3) unsigned not NULL auto_increment,
' ParentID ' tinyint (3) unsigned not NULL default ' 0 ',
' topic ' varchar default NULL,
PRIMARY KEY (' id '),
KEY ' ParentID ' (' ParentID ')
) Type=myisam;
INSERT into ' tree1 ' (' id ', ' parentid ', ' topic ') VALUES
(1, 0, ' tree 1 '),
(2,0, ' Tree 2 '),
(3,0, ' Tree 3 '),
(4,2, ' Tree 2-1 '),
(5,4, ' Tree 2-1-1 '),
(6,2, ' Tree 2-2 '),
(7,1, ' Tree 1-1 '),
(8,1, ' Tree 1-2 '),
(9,1, ' Tree 1-3 '),
(10,8, ' Tree 1-2-1 '),
(11,7, ' Tree 1-1-1 '),
(12,11, ' tree 1-1-1-1 ');
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Field description
ID, ID number of the record
ParentID, the record's parent record ID (0 is the root record)
Topic, the display title of the record
Show programs
Order Tree:
PHP Code:--------------------------------------------------------------------------------
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/* Database Connection * *
Mysql_connect ();
mysql_select_db (' tree ');
/* Tree Display recursive function * *
function tree ($parentid = 0) {
/* Execute SQL query, get the title and id*/of the record
$sql = "Select Topic,id from tree1 where parentid = $parentid ORDER by ID ASC";
$rs = mysql_query ($sql);
* * Indent/
Echo ("<ul>");
while ($ra = Mysql_fetch_row ($rs)) {
/* Display Record title * *
Echo (' <li> '. $ra [0]. </li> ');
/* Recursive call * *
Tree ($ra [1]);
}
Echo ("</ul>");
}
Tree ();
?>
--------------------------------------------------------------------------------
Reverse Tree:
PHP Code:--------------------------------------------------------------------------------
?
/* Database Connection * *
Mysql_connect ();
mysql_select_db (' tree ');
/* Tree Display recursive function * *
function tree ($parentid = 0) {
/* Execute SQL query, get the title and id*/of the record
$sql = "Select Topic,id from tree1 where parentid = $parentid order BY id DESC";
$rs = mysql_query ($sql);
* * Indent/
Echo ("<ul>");
while ($ra = Mysql_fetch_row ($rs)) {
/* Display Record title * *
Echo (' <li> '. $ra [0]. </li> ');
/* Recursive call * *
Tree ($ra [1]);
}
Echo ("</ul>");
}
Tree ();
?>
--------------------------------------------------------------------------------
Insert Data Program
PHP Code:--------------------------------------------------------------------------------
?
/* Database Connection * *
Mysql_connect ();
mysql_select_db (' tree ');
$sql = "INSERT into trees (Topic,parentid) VALUES (' Tree 3-1 ', 3);";
mysql_query ($sql);
?>
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2. Sort Field Method
This method is achieved by adding a field in the data structure that marks the ordinal position of the entire tree. The characteristic is the display speed and the efficiency is high. However, in the case of the complex structure of a single tree, the data write efficiency is insufficient. Moreover, the algorithm of inserting and deleting records is too complex, so it is usually arranged in reverse order.
Data structure (take MySQL as an example)
Code:--------------------------------------------------------------------------------
CREATE TABLE ' Tree2 ' (
' ID ' tinyint (3) unsigned not NULL auto_increment,
' ParentID ' tinyint (3) unsigned not NULL default ' 0 ',
' Rootid ' tinyint (3) unsigned not NULL default ' 0 ',
' Layer ' tinyint (3) unsigned not NULL default ' 0 ',
' Orders ' tinyint (3) unsigned not NULL default ' 0 ',
' topic ' varchar default NULL,
PRIMARY KEY (' id '),
KEY ' ParentID ' (' ParentID '),
KEY ' Rootid ' (' Rootid ')
) Type=myisam
INSERT into ' tree2 ' (' id ', ' parentid ', ' rootid ', ' layer ', ' orders ', ' topic ') VALUES
(1,0,1,0,0, ' tree 1 '),
(2,0,2,0,0, ' Tree 2 '),
(3,0,3,0,0, ' Tree 3 '),
(4,2,2,1,2, ' Tree 2-1 '),
(5,4,2,2,3, ' Tree 2-1-1 '),
(6,2,2,1,1, ' Tree 2-2 '),
(7,1,1,1,4, ' Tree 1-1 '),
(8,1,1,1,2, ' Tree 1-2 '),
(9,1,1,1,1, ' Tree 1-3 '),
(10,8,1,2,3, ' Tree 1-2-1 '),
(11,7,1,2,5, ' Tree 1-1-1 '),
(12,11,1,3,6, ' tree 1-1-1-1 ');
--------------------------------------------------------------------------------
Show programs
PHP Code:--------------------------------------------------------------------------------
?
/* Database Connection * *
Mysql_connect ();
mysql_select_db (' tree ');
/* Select all root record ID * *
$sql = "SELECT id from tree2 where parentid = 0 ORDER BY id DESC";
$rs = mysql_query ($sql);
Echo ("<ul>");
$lay = 0;
while ($ra = Mysql_fetch_row ($rs)) {
Echo ("<ul>");
/* Select All records for this tree and sort by orders field
$sql = "Select Topic,layer from tree2 where rootid = $ra [0] Order by orders";
$rs 1 = mysql_query ($sql);
while ($ra 1 = mysql_fetch_row ($rs 1)) {
/* Indent Display * *
if ($ra 1[1]> $lay) {
Echo (Str_repeat ("<ul>", $ra 1[1]-$lay));
}elseif ($ra 1[1]< $lay) {
Echo (Str_repeat ("</ul>", $lay-$ra 1[1]);
}
/* Record Display * *
Echo ("$ra 1[1]> $lay");
Echo ("<li> $ra 1[0]</li>");
$lay = $ra 1[1];
}
Echo ("</ul>");
}
Echo ("</ul>");
?>
--------------------------------------------------------------------------------
Insert Data Program
PHP Code:--------------------------------------------------------------------------------
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/* Database Connection * *
Mysql_connect ();
mysql_select_db (' tree ');
/* Insert Root record * *
$sql = "INSERT into TREE2 (topic) VALUES (' Tree 5 ')";
mysql_query ($sql);
$sql = "Update tree2 set Rootid = id where id =". mysql_insert_id ();
mysql_query ($sql);
/* Insert Child record * *
$parentid = 5;//Parent Record ID
/* Remove root record ID, parent record indent level, parent record order position
$sql = "Select Rootid,layer,orders from tree2 where id = $parentid";
List ($rootid, $layer, $orders) = Mysql_fetch_row (mysql_query ($sql));
/* The orders value recorded after the insertion position is updated * *
$sql = "Update tree2 Set orders = orders + 1 where orders > $orders";
mysql_query ($sql);
/* Insert Record * *
$sql = "INSERT into Tree2 (rootid,parentid,orders,layer,topic) VALUES ($rootid, $parentid,". $orders + 1). ",". ($layer + 1). ", ' Tree 2-1-1-2 ')";
mysql_query ($sql);? >
