Problem with: Duplicate values in array when query is run

Question

When I run the query below I keep getting the values twice. The array holds [1,2,1,2] and it should hold only values [1,2]. Could someone explain to me why I get the duplicate values?

$grusnro = 0;

while (!empty($grus[$grusnro ]))
{
  $catid="SELECT cat_id FROM  catgroup WHERE group_id='$grus[$grusnro]'";
  $catidsult=mysql_query($catid);

  while($grunamerow = mysql_fetch_array($catidsult, MYSQL_ASSOC))
  { 
    $catgroup[]=$grunamerow['cat_id'];  
  }

  $grusnro = $grusnro +1;
}

When I run from command-line I get the result [1,2]. I have checked that the group_id values are only once in the $grus array. So why the duplicates?

can you try print_r($grus) at the begining of this code to see what is the content of that array? And I would also print $grusnro at end of the first while loop to see if the value is incrementing up till 3. — Gabriel Spiteri
– Gabriel Spiteri, Commented May 19, 2011 at 9:25
To remove dupplicate values of an array, you may also use array_unique. Now, if Emil solution works as you pointed out, can you accept his solution? — Carlos Campderrós
– Carlos Campderrós, Commented May 19, 2011 at 9:58

Emil Vikström · Accepted Answer · 2011-05-19 09:17:37Z

2

I propose this simplified version of your code, which will perform much better:

$catgroup = array(); //Making sure $catgroup is an empty array
if(!empty($grus)) {
  //Fetch all groups in the same query
  $grusids = implode("','", $grus);
  $catid = 'SELECT DISTINCT cat_id FROM catgroup WHERE group_id IN(\''.$grusids.'\')';
  $catidsult = mysql_query($catid);
  while($grunamerow = mysql_fetch_array($catidsult, MYSQL_ASSOC))
  {   
    $catgroup[] = $grunamerow['cat_id'];
  }
}

Notice the use of the DISTINCT keyword in SQL to only fetch unique cat_ids.

answered May 19, 2011 at 9:17

Emil Vikström

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