Question

I am planning to create a multi select drop down or multi select check box form element in php. But with a parent child menu item relation ship.

Ex: So I have got three separate tables tbl_branch, tbl_area, tbl_region and 2 more tables for the mapping tbl_regiontoarea and tbl_areatobranch. Now I need a multi select or multi check box which looks some thing like this:

Branch 1
 Area 1
   Region 1
   Region 2
 Area 2
   Region 3
   Region 4
   Region 7
   Region 9
 Area 5
 Area 7
   Region 8

Branch 2 
 Area 3

Branch 3
Branch 4
Branch 5
 Area 6
   Region 10
 Area 2

So as you would have guessed it, Branch is the top most in the hierarchy and region is the lowermost i.e. Branch is the parent. I would like it to loop until it finds children for it. Once it stops finding any children it would move on to next parent item in the array.

I am very bad with arrays, and forming complex sql queries and hence was looking forward to have some starting direction on how to do this. I would really appreciate if some one could help me with the same.

Thanks in advance

Answer 1

I suggest you give this a read

http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/

I’ve set up a tree of near identical data and using the methods suggested in the above document make the issue significantly simpler especially when it comes to determining parents and siblings down to n levels.

The short version is that you assign a number on ‘left’ and ‘right’ of each node, and using that you can then select segments of the tree very efficiently. The more long winded version is in that article, and explains it far more thoroughly than I can and includes useful MySQL code.

Here’s a potential outline for your main table

treeTable (
    // ID field
    id INT UNSIGNED PK AI,
    // Fields for branching
    lft INT UNSIGNED,
    rgt INT UNSIGNED,
    // ID fields for the specific types
    leafType ENUM('Branch','Area','Region'),
    leafID INT UNSIGNED,
    leafName VARCHAR
)

UNIQUE INDEX (leafType,leafID)

If you need specific data for each type then you could create seperate tables for them but the above would let you create your tree, map out the id’s and allow relationships to be stored along with a display name.

Of course the more data you can normalise between each leafType the better, ideally they are all effectively the same type of data after all as they are all a geographic subsection

Taking a sample of your data as example

Branch 3
Branch 4
Branch 5
 Area 6
   Region 10
 Area 2

you might end up with table such as

id  lft rgt leafType    leafID  
1   1   2   'Branch'    3   
2   3   4   'Branch'    4
3   5   12  'Branch'    5
4   6   9   'Area'      6
5   7   8   'Region'    10
6   10  11  'Area'      2

Queries for how to insert etc can be found in the linked article, i.e. (quoted verbatim from http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/)

LOCK TABLE nested_category WRITE;

SELECT @myLeft := lft FROM nested_category

WHERE name = '2 WAY RADIOS';

UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myLeft;
UPDATE nested_category SET lft = lft + 2 WHERE lft > @myLeft;

INSERT INTO nested_category(name, lft, rgt) VALUES('FRS', @myLeft + 1, @myLeft + 2);

UNLOCK TABLES;

And then a SELECT can illustrate the tree (again verbatim from the source)

SELECT CONCAT( REPEAT( ' ', (COUNT(parent.name) - 1) ), node.name) AS name
FROM nested_category AS node,
        nested_category AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
GROUP BY node.name
ORDER BY node.lft;

Field/table names in the 2 above are of course unchanged, but you can update the table/field names as necessary

Following my latest comment, below is the definition for my stored procedure I use for inserting new rows

CREATE PROCEDURE `addOptionalExtraToTree`(inParentOptionID INT,inOptionName VARCHAR(40),inLeafType VARCHAR(20))
BEGIN
    DECLARE myRight INT UNSIGNED DEFAULT 0;

    SELECT optionalExtra_tree_right-1
    INTO myRight
    FROM optionalExtras
    WHERE optionalExtraID = inParentOptionID;

    IF myRight = 0 THEN
        SELECT COALESCE(MAX(optionalExtra_tree_right),0)
        INTO myRight
        FROM optionalExtras;
    END IF;

    UPDATE optionalExtras 
    SET optionalExtra_tree_right = optionalExtra_tree_right + 2 
    WHERE optionalExtra_tree_right > myRight;

    UPDATE optionalExtras 
    SET optionalExtra_tree_left = optionalExtra_tree_left + 2 
    WHERE optionalExtra_tree_left > myRight;

    INSERT INTO optionalExtras (
        optionalExtra_name,
        optionalExtra_leaf_type,
        optionalExtra_tree_left,
        optionalExtra_tree_right
    ) VALUES (
        inOptionName,
        inLeafType,
        myRight + 1,
        myRight + 2
    );

    SELECT LAST_INSERT_ID() AS optionalExtraID;

END;

This is then called using calls such as the following

CALL addOptionalExtraToTree(0,'New root option','Region');
CALL addOptionalExtraToTree(4,'New child option','Area');