Question

i have a table named IMAGES in which there is attribute name img_ID which is the primary key,

there is another table called Favorites in which there are two attributes ‘img_ID’ & user_ID … img_ID serves as the foreign key to an image and user_ID serves as foreign key to the user

NOW i need details of from IMAGES of all the img_IDs from Favorites where user_ID is some x-value

this i could do like this, b.t.w i am using PHP & mySQL

$gett = mysql_query("SELECT img_ID FROM favorites WHERE user_ID='".$variable."'");

if( mysql_num_rows($gett) > 0 )
{
  while( $steps = mysql_fetch_assoc($gett) )
  {
     $res = mysql_query("SELECT * FROM images WHERE img_ID='".$steps['img_ID']."' ORDER BY img_Date");

         if( mysql_num_rows($res) > 0 )
         {
            while( $result= mysql_fetch_assoc($res) )
            {
               echo $result['img_Name'];
               echo $result['img_Desc'];
               echo $result['img_ext'];
            }
         else 
            echo "no images were found";
  }
}
else 
  echo "no favorites were found";

THE PSEUDO CODE will be like

RUN QUERY
for each img_ID where user_ID is this
    RUN QUERY    
    for each img_ID
        perform DISPLAY

This methodology has a flaw & a back-draw

FLAW       = the order which is on time stamp is destroyed

back-draw = there is a query in nested loop..

QUESTION: Can this all be done in with query? if Yes then How ?

Answer 1

Use a join:

select
  i.*
from
  favorites f
  join images i on f.img_id = i.img_id
where
  f.user_id = <user id>

Also, change your code to use mysqli and prepared statements with bind variables to both improve performance and eliminate the threat of sql injection attacks.