Question

disclaimer: I posted this on another site first

I have a table (res_table) that is about 200 columns wide. One of these columns is named “feature_lk”, and it consists of a string of numbers which are “|” delimited. The numbers stand for feature catagories which reside in another table named “features”

Thanks to this thread: http://www.kirupa.com/forum/showthread.php?t=224203 I figured out how to parse the features out!

Now my problem is how to look them up? I feel like I either need to join my two tables, but I’m not sure how, or I need to do a another select query for each of the features that I parse.. This is what I have to far (removed connection strings for posting purposes)

PHP Code:
<?php 
$sql = ("SELECT * FROM res_table"); 
$result = mysql_query($sql); 

while($row = mysql_fetch_array($result)) 
{ 
    $feature_string = $row['features_lk']; 
    $features = explode( '|', $feature_string ); 

    foreach( $features as $feature ) { 
        $feature = trim( $feature ); 
        echo $feature.': '; 

        $sql2 = "SELECT * from features where features.feature_id like $feature"; 
        $result2 = mysql_query($sql2); 
        while ($row2 = mysql_fetch_array($result2)) 
        { 
            $feat_desc = $row2['feature_description']; //this is another column in the features table 
            echo $feat_desc . '<br>'; 
        } 
    } 
    echo '<br>'; 
} 
?>

SO that works OK because when I run it, i’ll get about results that look like this:

13: None
62: Water Softener - Rented
71: Full
168: Barn
222: Storage Shed
226: Walkout
309: Detached
347: 2 Story
384: Attic Storage
439: Laundry Hook Up
466: Rural
476: Trees
512: School Bus
562: Mud Room
563: Pantry
2273: Septic Tank
643: Private Well

My question is: is there a better way to do this? There are about 10k rows in the main res_table with only a couple hundred hits, you can see that the number of select statements performed grows LARGE in no time at all.

I’m sure this is PHP + MySQL 101 stuff, but I’m just a beginner so any ideas? Thanks in advance.

Answer 1

When you are storing more than one piece of information in a column, your table is not normalized. Doing lookups on feature_lk will necessarily be slow and difficult. feature_lk should become its own table:

Table feature_lk:

• res_table_id FK to res_table
• feature_id FK to feature table
• primary key(res_table_id,feature_id)

Then your query is:

SELECT f.* from features f 
  JOIN feature_lk lk ON (f.id=lk.feature_id) 
  JOIN res_table r ON (lk.res_table_id=r.id);

One query only. No loop. No parsing out the features.

ETA

stored procedure for splitting an arbitrary length string by an arbitrary character

DELIMITER $$

DROP PROCEDURE IF EXISTS `dorepeat` $$
CREATE PROCEDURE `dorepeat`(in ToBeSplit LONGTEXT , in Splitter CHAR)
Begin

DECLARE TotalLength INT;
DECLARE SplitterPosition INT;
DECLARE SubstringLength INT;
DECLARE SubstringStart INT;

DROP Table if exists Split_Values;
CREATE temporary TABLE Split_Values (split varchar(255));

SET TotalLength = LENGTH(ToBeSplit);
SET SplitterPosition = LOCATE(Splitter, ToBeSplit);
SET SubstringStart = 1;

ss: WHILE SplitterPosition < TotalLength DO
        IF SplitterPosition!=0 THEN 
                SET SubstringLength = SplitterPosition - SubstringStart;
                Insert into Split_Values VALUES (SUBSTRING(ToBeSplit,SubstringStart,SubstringLength));
                SET SubstringStart = SplitterPosition+1;
                SET SplitterPosition = LOCATE(Splitter, ToBeSplit, SplitterPosition+1);
        ELSE
                Insert into Split_Values VALUES (SUBSTRING(ToBeSplit,SubstringStart));
                SET SplitterPosition=TotalLength;
        END IF;
END WHILE ss;
End $$

DELIMITER ;

Using dorepeat in another procedure makes temp table with res_table_id and each feature:

DELIMITER $$

DROP PROCEDURE IF EXISTS `multido` $$
CREATE PROCEDURE `multido`()
Begin
DECLARE done INT default 0;
DECLARE rt_id INT (10);
DECLARE features LONGTEXT;
DECLARE mycur cursor for select distinct res_table_id, feature_lk from res_table WHERE feature_lk!='';
DECLARE continue handler for sqlstate '02000' set done=1;
drop table if exists tmpfeatures;
create temporary table tmpfeatures( res_table_id int(10),  feature varchar(255));
open mycur;
repeat
  fetch mycur into rt_id,features;
  call dorepeat(features,'|');
  insert into tmpfeatures select rt_id, trim(split) from Split_Values;
until done end repeat;
close mycur;

End $$

DELIMITER ;