嵌套while循環中的SQL語句

Question

我正在為我們的IT部門編寫一份股票盤點申請，但我不確定自己的發展方式是否最佳。

我創建了一個“產品組”表和一個“產品”表，這些表與一個ID（一個產品組到許多產品）產品組關聯，例如LaserJet Pro 400，產品將是單個消耗品。.黑色，品紅色，青色等。

因此，發生的事情是我有一個while循環來顯示組，然后有一個嵌套的while循環來顯示該組內的產品。

我擔心的是很多sql語句急速發展，在此早期階段似乎沒有性能問題，但我不確定..是否可以接受？ 有沒有更好的辦法？

foreach ($_POST['BeginLocation'] as $key => $value) {$LocationID = $key;}

echo '<div class="nmform"><form name="StockTake" action="index.php" method="post" enctype="multipart/form-data">';

include "../DBCon/RDPNearMisses.php";

$GetProductGroups = sqlsrv_query($NMDB, "select distinct PD.ProductGroupID, PG.GroupName
                                        from [JobObservations].[dbo].[ITStk.Products] as PD
                                        inner join [JobObservations].[dbo].[ITStk.ProductGroups] as PG on PD.ProductGroupID = PG.ProductGroupID
                                        where PD.LocationID = $LocationID");

                       if( $GetProductGroups === false ) {
                           if( ($errors = sqlsrv_errors() ) != null) {
                               foreach( $errors as $error ) {
                                   echo "SQLSTATE: ".$error[ 'SQLSTATE']."<br />";
                                   echo "code: ".$error[ 'code']."<br />";
                                   echo "message: ".$error[ 'message']."<br />";
                               }
                           }
                       }

                       while ($row = sqlsrv_fetch_array($GetProductGroups)) {echo '<h4>'.$row['GroupName'].'</h4>';
                                                $ProductGroupID = $row['ProductGroupID'];

                                                $GetProducts = sqlsrv_query($NMDB, "select PD.ProductID, PD.ProductGroupID, PD.ProductCode, PD.ProductDescription
                                                from [JobObservations].[dbo].[ITStk.Products] as PD
                                                inner join [JobObservations].[dbo].[ITStk.ProductGroups] as PG on PD.ProductGroupID = PG.ProductGroupID
                                                inner join [JobObservations].[dbo].[ITStk.Locations] as LC on PD.LocationID = LC.LocationID
                                                where PD.LocationID = $LocationID
                                                and PD.ProductGroupID = $ProductGroupID
                                                order by LC.LocationDescription asc, PG.GroupName asc, PD.ProductCode asc");

                                                if( $GetProducts === false ) {
                                                    if( ($errors = sqlsrv_errors() ) != null) {
                                                        foreach( $errors as $error ) {
                                                            echo "SQLSTATE: ".$error[ 'SQLSTATE']."<br />";
                                                            echo "code: ".$error[ 'code']."<br />";
                                                            echo "message: ".$error[ 'message']."<br />";
                                                        }
                                                    }
                                                }
                                                echo '<table><th>Code</th><th>Description</th><th>Qty</th>';
                                                while ($row1= sqlsrv_fetch_array($GetProducts)) {echo '<tr><td>'.$row1['ProductCode'].'</td><td>'.$row1['ProductDescription'].'</td><td><select name="'.$row1['ProductID'].'"><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option></select></td></tr>';}
                                                echo '</table>';


                       }
                       echo '<input type="Submit" name="SubmitStock"></form>';
                       sqlsrv_close($NMDB);
         echo '</div>';

Answer 1

雖然數據很小，每個位置的組數很小，但是您可能不會注意到差異，但是隨着每個位置的組數變化，您可能需要考慮切換到1個查詢和while循環：

SELECT DISTINCT
    PD.ProductID,
    PG.GroupName,
    PD.ProductGroupID,  
    PD.ProductCode,
    PD.ProductDescription
FROM [JobObservations].[dbo].[ITStk.Products] AS PD
INNER JOIN [JobObservations].[dbo].[ITStk.ProductGroups] AS PG ON PD.ProductGroupID = PG.ProductGroupID
INNER JOIN [JobObservations].[dbo].[ITStk.Locations] AS LC ON PD.LocationID = LC.LocationID
WHERE PD.LocationID = $LOCATIONID;

它將很好地工作，因為它將為您提供一個記錄集，其中包含未使用的GroupName以及您在表中使用的產品ID和產品描述。

此外，除非將表ITStk.Locations僅僅是為了限制Locations表中實際存在LocationID記錄，否則就不需要在此處聯接它。 您不使用任何字段來限制結果集或SELECT。

幾乎每當您發現自己抓住一個記錄集並在讀取/循環記錄集時發出更多的SQL時，您都可以將其變成一條SQL語句。

為了讓您的GroupName作為表頭，在您的while循環中，您可以執行以下操作（請原諒，自從我寫PHP已有幾年了）：

$GetProductGroups = sqlsrv_query($NMDB, "SELECT DISTINCT
                                        PD.ProductID,
                                        PG.GroupName,
                                        PD.ProductGroupID,  
                                        PD.ProductCode,
                                        PD.ProductDescription
                                    FROM [JobObservations].[dbo].[ITStk.Products] AS PD
                                    INNER JOIN [JobObservations].[dbo].[ITStk.ProductGroups] AS PG ON PD.ProductGroupID = PG.ProductGroupID
                                    INNER JOIN [JobObservations].[dbo].[ITStk.Locations] AS LC ON PD.LocationID = LC.LocationID
                                    WHERE PD.LocationID = $LOCATIONID
                                    ORDER BY GroupName;");

if( $GetProductGroups === false ) {
   if( ($errors = sqlsrv_errors() ) != null) {
       foreach( $errors as $error ) {
           echo "SQLSTATE: ".$error[ 'SQLSTATE']."<br />";
           echo "code: ".$error[ 'code']."<br />";
           echo "message: ".$error[ 'message']."<br />";
       }
   }
}

while ($row = sqlsrv_fetch_array($GetProductGroups)) {

    /*If the groupname of the current record is different then the last record's group name (notice order by on query) then echo out the header and start a new table*/
    if ( $groupname != $row['GroupName']) {
        echo '<h4>'.$row['GroupName'].'</h4>';
        echo '<table><th>Code</th><th>Description</th><th>Qty</th>';
    }

    /*echo out the row into the table*/
    echo '<tr><td>'.$row['ProductCode'].'</td><td>'.$row['ProductDescription'].'</td><td><select name="'.$row1['ProductID'].'"><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option><option>0</option></select></td></tr>';


    /*again if we started a new table because the groupname is new in the recordset, then close the table*/
    if ( $groupname != $row['GroupName']) {         
        echo '</table>';
    }
    /*Capture group name for future iterations*/    
    $groupname = $row['GroupName'];

}

echo '<input type="Submit" name="SubmitStock"></form>';
sqlsrv_close($NMDB);
echo '</div>';