CODEWITHSUNDEEP
phpmysqldatabasesorting
TOL
TOL

Reputation: 3

MYSQL: select parent sorted alphabetically grouped with children sorted alphabetically

I've made a simple table to understand parent-child relationship, but I don't seem to get proper results. I want to sort it

  1. first alphabetically by 'name' field, only those who have no parent (parent_id==0)
  2. BUT, whenever there are child rows for the parent, they should be printed after the parent, also sorted alphabetically by name.

Example table:

============================================================

CREATE TABLE IF NOT EXISTS `test` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `parent_id` int(11) NOT NULL DEFAULT '0',
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=9 ;

--
-- Dumping data for table `test`
--

INSERT INTO `test` (`id`, `parent_id`, `name`) VALUES
(1, 4, 'Zorg'),
(2, 0, 'Woordolack'),
(3, 4, 'Akriller'),
(4, 0, 'Metabrusher'),
(5, 2, 'Intersplitter'),
(6, 0, 'Beaverbrain'),
(7, 4, 'Torgeoruos'),
(8, 2, 'Deptezaurus');

============================================================

Here is what I want to output to a web browser using PHP:

 Beaverbrain
 Metabrusher
 -> Akriller
 -> Torgeoruos
 -> Zorg
 Woordolack
 -> Deptezaurus
 -> Intersplitter

============================================================

I should say that this is a sample table just to show the idea, so it can be modified in any way to get the proper result.

Upvotes: 0

Views: 1453

Answers (4)

MigueLito
MigueLito

Reputation: 11

Try this solution:

SELECT
    A.id,
    A.name
FROM 
    `test` AS A LEFT JOIN `test` AS B ON A.`parent_id` = B.`id`
GROUP BY
    A.`id`
ORDER BY
    IFNULL(B.`name`, A.`name`), 
    COALESCE(A.`parent_id`, A.`id`), 
    A.`parent_id` != 0, 
    A.`name`;

Upvotes: 1

1mr3yn
1mr3yn

Reputation: 74

On managing hierarchical data, You can use a simple PHP recursive function instead,

 function DisplayTree( $parent , $depth)     {                                                                                                    
    $sql = $this->db->query("SELECT id,name FROM '$table' WHERE parent_id = '$parent'");

      foreach($sql->result() as $field ) {  
        print "<fieldset style=\"margin-left:$depth%; width:300px\">";  
            print $field->name;
        print "</fieldset>";

        $this->DisplayTree( $field->code , $depth+8 );           
     }  

   }

Upvotes: 0

Tin Tran
Tin Tran

Reputation: 6202

You can try this query

SELECT IF(child = '',parent,CONCAT('->',child)) as value 
FROM
    (SELECT parent.name as parent,child.name as child
     FROM test parent 
       INNER JOIN 
       (SELECT id,parent_id,name FROM test 
        UNION 
        SELECT null,id,'' FROM test
        WHERE parent_id = 0)child
     WHERE parent.parent_id = 0
     AND child.parent_id = parent.id
     ORDER BY parent,child
     )parent_child

sqlFiddle

What the query does is INNER JOIN test with test and find out which are parent and child. The inner UNION SELECT null,id,'' FROM test WHERE parent_id = 0 creates an empty child(ren) for display purposes. Then the outter SELECT sees if the child is '' it prints out parent, otherwise it concats -> in front of child. and so you get your result like how you wanted.

The below version might be a little faster. Since we'll just create parents with NULL child instead of using children as part of INNER JOIN (above).

SELECT IF(child IS NULL,parent,CONCAT('->',child)) as value 
FROM
 (SELECT parent.name as parent,child.name as child
    FROM test parent 
   INNER JOIN test child ON child.parent_id = parent.id
   WHERE parent.parent_id = 0
  UNION
  SELECT test.name as parent,NULL as child    #This creates a NULL child row
    FROM test WHERE test.parent_id = 0        #for parent display purpose
  ORDER BY parent,child
 )parent_child

sqlFiddle

I would however use the below query instead and inside PHP, check to see if the isParent flag is 1 or 0 and then show the appropriate fields.

SELECT 0 as isParent,parent.name as parent,child.name as child,
       parent.id as parentId,child.id as childId
  FROM test parent 
 INNER JOIN test child ON child.parent_id = parent.id
 WHERE parent.parent_id = 0
UNION
SELECT 1 as isParent,test.name as parent,NULL as child,
       test.id as parentId,NULL as childId
  FROM test WHERE test.parent_id = 0       
ORDER BY parent,child

sqlFiddle

Upvotes: 3

Kamehameha
Kamehameha

Reputation: 5473

Using a couple of simple queries in PHP,

    $r1 = $db->query("select * from test where parent_id = 0 order by name asc") or die('err in q1');
    while($arr1 = $r1->fetch_assoc()){
            $parent = $arr1['name'];
            $parent_id = $arr1['id'];
            echo $parent
            $r2 = $db->query("select * from test where parent_id = $parent order by name asc") or die('err in q2');
            while($arr2 = $r2->fetch_assoc()){
                 $child = $arr2['name'];
                 echo $child."<br />";
            }
    }

Upvotes: 0

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