How to get multiple columns from the same table

Question

I have 4 $queries concatenated like below:

this select one attribute called shape:

    $sql = "
SELECT p.`ID` AS 'Product ID', 
       p.`post_title` AS 'Product Name', 
       t.`term_id` AS 'Attribute Value ID', 
       REPLACE(REPLACE(tt.`taxonomy`, 'pa_', ''), '-', ' ') AS 'Attribute Name', 
       t.`name` AS 'Shape' 
       FROM `wp_posts` AS p 
       INNER JOIN `wp_term_relationships` AS tr ON p.`ID` = tr.`object_id` 
       INNER JOIN `wp_term_taxonomy` AS tt ON tr.`term_taxonomy_id` = tt.`term_id` AND tt.`taxonomy` LIKE 'pa_shape%'
       INNER JOIN `wp_terms` AS t ON tr.`term_taxonomy_id` = t.`term_id` 
       WHERE p.`post_type` = 'product' 
       AND p.`post_status` = 'publish' ORDER BY p.`ID`";

To select the "clarity" from the same table and same column:

$sql .= "SELECT p.`ID` AS 'Product ID', 
       p.`post_title` AS 'Product Name', 
       t.`term_id` AS 'Attribute Value ID', 
       REPLACE(REPLACE(tt.`taxonomy`, 'pa_', ''), '-', ' ') AS 'Attribute Name', 
       t.`name` AS 'Clarity' 
       FROM `wp_posts` AS p 
       INNER JOIN `wp_term_relationships` AS tr ON p.`ID` = tr.`object_id` 
       INNER JOIN `wp_term_taxonomy` AS tt ON tr.`term_taxonomy_id` = tt.`term_id` AND tt.`taxonomy` LIKE 'pa_clarity%'
       INNER JOIN `wp_terms` AS t ON tr.`term_taxonomy_id` = t.`term_id` 
       WHERE p.`post_type` = 'product'"

and there are few other select statement such as this one. I tried to merged them together but I couldn't. Now I am running multiple queries and hoping to get it work with the following but I am not returning any values:

$output .= "<table><thead><tr><th>Carat</th><th>Color</th><th>Cut</th><th>Shape</th><th>Clarity</th></tr></thead><tbody>";


if (mysqli_multi_query($con,$sql))
{
  do
    {
    // Store first result set
    if ($result=mysqli_store_result($con)) {
      // Fetch one and one row
      while ($row=mysqli_fetch_row($result))
        {
        $output .= "<td>" . $row['Carat'] . "</td><td>" . $row['Color'] . "</td><td>" . $row['Cut'] . "</td><td>" . $row['Shape'] . "</td><td>" . $row['Clarity'] . "</td></tr>" ;
                }
              // Free result set
              mysqli_free_result($result);
              }
            }
          while (mysqli_next_result($con));
        }

        mysqli_close($con);
        $output .= "</table>";



        return $output;

The variable output is for a bigger function and how I output them on my page. Please any suggestion on why the mysqli_multi_query() is not working? or if I could merge queries like that into one. All helps are appreciated in advance.

Answer 1

If you are just fetching separate attributes in different queries then you can achieve that by modifying ON clause in the join.

1: One record per product per attribute

SELECT 
    p.`ID` AS 'Product ID', 
    p.`post_title` AS 'Product Name', 
    t.`term_id` AS 'Attribute Value ID', 
    REPLACE(REPLACE(tt.`taxonomy`, 'pa_', ''), '-', ' ') AS 'Attribute Name', 
    t.`name` AS 'Attribute Value' 
 FROM `wp_posts` AS p 
 INNER JOIN `wp_term_relationships` AS tr ON p.`ID` = tr.`object_id` 
 INNER JOIN `wp_term_taxonomy` AS tt ON tr.`term_taxonomy_id` = tt.`term_id` 
    AND (tt.`taxonomy` LIKE 'pa_clarity%' OR tt.`taxonomy` LIKE 'pa_shape%') -- If require add more attribute here and you are good
 INNER JOIN `wp_terms` AS t ON tr.`term_taxonomy_id` = t.`term_id` 
 WHERE p.`post_type` = 'product';

Output:
+-----------------------------------------------------------------------------------+
| Product ID | Product Name | Attribute Value ID | Attribute Name | Attribute Value |
| p1         | p1_name      | 10                 | Clarity        | Not clear       |
| p1         | p1_name      | 11                 | Shape          | Square          |
| p2         | p2_name      | 10                 | Clarity        | Clear           |
| p2         | p2_name      | 11                 | Shape          | Circle          |
+-----------------------------------------------------------------------------------+

Note: If you have ORDER BY or GROUP BY for a particular attribute only, it won't work here. If you apply it will be applicable for all attributes which you have included in this join.

2: One record per product, all attributes as columns

SELECT 
    p.`ID` AS 'Product ID', 
    p.`post_title` AS 'Product Name', 
    GROUP_CONCAT(IF(tt.`taxonomy` LIKE 'pa_clarity%', t.`name`, NULL)) AS 'Clarity',
    GROUP_CONCAT(IF(tt.`taxonomy` LIKE 'pa_shape%', t.`name`, NULL)) AS 'Shape' -- Add more attributes in same way
 FROM `wp_posts` AS p 
 INNER JOIN `wp_term_relationships` AS tr ON p.`ID` = tr.`object_id` 
 INNER JOIN `wp_term_taxonomy` AS tt ON tr.`term_taxonomy_id` = tt.`term_id` 
    AND (tt.`taxonomy` LIKE 'pa_clarity%' OR tt.`taxonomy` LIKE 'pa_shape%') -- If require add more attribute here and you are good
 INNER JOIN `wp_terms` AS t ON tr.`term_taxonomy_id` = t.`term_id` 
 WHERE p.`post_type` = 'product'
 GROUP BY p.`ID`;

Output:
+-------------------------------------------------+
| Product ID | Product Name | Clarity   | Shape   |
| p1         | p1_name      | Not clear | Circle  |
| p2         | p2_name      | clear     | Square  |
+-------------------------------------------------+