PHP

Step 3: Finishing the Panel

We have built a satisfactory component. However, one problem identified earlier still remains. The first-listed wine appears twice. In this case it is because there are two inventory entries for the same wine, with the only difference being the prices. Of course, our user will pick the cheapest.

Fixing the queries

To address the inventory problem-where a wine appears multiple times in the front panel if there are multiple inventories of that wine-you need to modify the initial query.

Only one row should be produced per wine, not one per inventory. To do this, remove the inventory table attributes from the SELECT statement and add a DISTINCT to remove the duplicates. However, you can't remove the inventory table fully from the query, because you still need to ORDER BY date_added to display the newest wines added to our winestore cellar. The query is now as follows:

$query = "SELECT wi.winery_name,
                  w.year,
                  w.wine_name,
                  w.description,
                  w.wine_id
          FROM wine w, winery wi, inventory i
          WHERE w.description != \"\"
          AND w.winery_id = wi.winery_id
          AND w.wine_id = i.wine_id
          GROUP BY winde-id
          ORDER BY i.date_added DESC LIMIT 3";

With this modified query, one entry is produced per wine. However, having removed the inventory attributes, you no longer have the pricing information.

You need another query and some script reorganization. Example 4-11 shows a substantially rewritten script that adds a second new function, showPricing( ), that has the correct inventory handling. The function showPricing( ) has a similar structure to showVarieties( ).

showPricing( ) adds the cheapest inventory price to the panel for each wine and uses a new query. The query is:

$query =  SELECT min (cost), min (case_cost)
          FROM inventory
          WHERE wine_id = $wineID;
Example 4-11. Script with correct inventory handling for the latest wine display
<!DOCTYPE HTML PUBLIC
               "-//W3C//DTD HTML 4.0 Transitional//EN"
               "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
  <title>Alexa and Dave's Online Wines</title>
</head>
<body bgcolor="white">
<h1>New Wines</h1>
Here are three top new wines we have in stock
<br><br>
<?php
   include 'db.inc';
   include 'error.inc';
   // Print out the varieties for a wineID
   function showVarieties($connection, $wineID)
   {
      // Find the varieties of the current wine,
      // and order them by id
      $query = "SELECT gv.variety
                FROM grape_variety gv,
                     wine_variety wv, wine w
                WHERE w.wine_id = wv.wine_id
                AND wv.variety_id = gv.variety_id
                AND w.wine_id = $wineID
                ORDER BY wv.id";
      // Run the query
      if (!($result = @ mysql_query($query, $connection)))
         showerror(  );
      // Retrieve the varieties ...
      while ($row = @ mysql_fetch_array($result))
         // ... and print each one
         echo " " . $row["variety"];
   }
   // Print out the pricing information
   function showPricing($connection, $wineID)
   {
      // Find the cheapest prices for the wine,
      $query =  SELECT min (cost), min (case_cost)
                FROM inventory
                WHERE wine_id = $wineID
      // Run the query
      if (!($result = @ mysql_query($query, $connection)))
         showerror(  );
      // Retrieve the cheapest price
      $row = @ mysql_fetch_array($result);
      // Print the pricing information
      echo "\n<tr>\n\t<td bgcolor=\"gray\">" .
           "<b>Our price: </b>" .
           $row["min(case_cost)"] .
           "(" . $row["min(cost)"] . " a dozen)";
      // Calculate the saving for 12 or more bottle
      $dozen_saving = $row["min(cost)"] - ($row["min(case_cost)"]/12);
      // If there's a saving, show what it is
      if ($dozen_saving > 0)
         printf(" Save <b>%.2f</b> per bottle when
                 buying a dozen\n", $dozen_saving);
      echo "</td>\n</tr>";
   }
   // ---------
   $query = "SELECT wi.winery_name,
                     w.year,
                     w.wine_name,
                     w.description,
                     w.wine_id
             FROM wine w, winery wi, inventory i
             WHERE w.description != \"\"
             AND w.winery_id = wi.winery_id
             AND w.wine_id = i.wine_id
             GROUP BY w.wine_id
             ORDER BY i.date_added DESC LIMIT 3";
   // Open a connection to the DBMS
   if (!($connection = @ mysql_connect($hostName,
                                       $username,
                                       $password)))
      die("Could not connect to database");
   if (!mysql_select_db("winestore", $connection))
      showerror(  );
   // Run the query created above on the database through
   // the connection
   if (!($result = @ mysql_query ($query, $connection)))
      showerror(  );
   echo "\n<table border=\"0\">";
   // Process the three new wines
   while ($row = @ mysql_fetch_array($result))
   {
      // Print a heading for the wine
      echo "\n<tr>\n\t<td bgcolor=\"maroon\">" .
           "<b><font color=\"white\">" .
           $row["year"] . " " .
           $row["winery_name"] . " " .
           $row["wine_name"] . " ";
      // Print the varieties for this wine
      showVarieties($connection, $row["wine_id"]);
      echo "</font></b></td>\n</tr>";
      // Print the wine review
      echo "\n<tr>\n\t<td bgcolor=\"silver\">" .
           "<b>Review: </b>" .
           $row["description"] .
           "</td>\n</tr>";
      // Show the pricing information
      showPricing($connection, $row["wine_id"]);
      // Blank row for presentation
      echo "\n<tr>\n\t<td></td>\n</tr>";
   }
   echo "\n</table>\n";
   if (!mysql_close($connection))
      showerror(  );
?>
</body>
</html>

The difference in producing price information is that the code doesn't retrieve all rows in the result set with a loop. Rather, it retrieves only one row-the row representing the cheapest inventory. It then outputs the min(cost) and min(case_cost) as previously, with the same dozen_saving calculation.

The final panel, with correct inventory handling, calculations, and varieties, is shown in Figure 4-5.

Figure 4-5. Panel with correct inventory handling, calculations, and varieties
figs/wda_0405.gif

by BrainBellupdated
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