Question

我的数据库中有两个表 - ＆＃34; region＆＃34;和＆＃34;吸引力＆＃34;。我做了一个JOIN查询，它将从这两个数据中获取数据，而我正在显示它。这是我的代码：

$regionsId = $_GET['region']; 

//$sql    = "SELECT `RegionID`, `RegionName`  FROM `region` WHERE `RegionID`='$regionsId'";
//$sql    = "SELECT `AttractionID`, `Name`, `imglink2`  FROM `attractions` WHERE `RegionID`='$regionsId'";

$sql ="SELECT * 
FROM region
INNER JOIN attractions WHERE region.RegionID = '$regionsId' AND attractions.RegionID = '$regionsId'";


$result = mysql_query($sql, $link);

if (!$result) {
    echo "DB Error, could not query the database\n";
    echo 'MySQL Error: ' . mysql_error();
    exit;
}



while ($row = mysql_fetch_assoc($result)) {

    echo $row['RegionName']; 

    echo "<a href='attraction.php?village=" . $row['AttractionID'] . "'>" .  "<br />" .
          $row['Name']  .
           "<br />" .

         "<img src='" . $row['imglink2'] . "' height='130' width='150'> 

       </a>";



}





mysql_free_result($result);



 ?>

我的问题是当我显示echo $ row [＆＃39; RegionName＆＃39;];我显示的每个景点都会多次显示。我怎样才能使它只显示一次？谢谢。

Answer 1

尝试GROUP BY

 $sql ="
SELECT *
FROM region 
LEFT JOIN attractions ON region.RegionID = attractions.RegionID 
WHERE region.RegionID = '$regionsId'
  AND attractions.RegionID = '$regionsId'
GROUP BY region.RegionID" ;

Answer 2

使用此：

$sql = "SELECT DISTINCT *
FROM region 
  LEFT JOIN attractions ON region.RegionID = attractions.RegionID 
WHERE region.RegionID = '$regionsId'
  AND attractions.RegionID = '$regionsId'
GROUP BY region.RegionID";

Answer 3

评论有点长。 SQL将以表格格式返回值，所有“单元格”完全填入：

region     attraction
   A          1
   A          2
   A          3
   B          1
   B          5

如果你想要这种形式：

   A           1,2,3
   B           1,5

然后数据库是合适的：

SELECT r.*, group_concat(a.AttractionId)
FROM region r LEFT JOIN
     attractions a
     ON r.RegionID = a.RegionID 
WHERE r.RegionID = '$regionsId'
GROUP BY r.RegionID;

如果你想要这种形式：

region     attraction
   A          1
              2
              3
   B          1
              5

然后你应该在应用层进行工作。可以在数据库中进行设置，但它在处理表时“违反”SQL的性质。并且，在显示结果时循环显示结果非常容易。

Answer 4

最简单的方法是将order by RegionName添加到您的查询中，然后更改代码以监视区域更改并仅在发生更改时显示，如下所示：

$prevRegionName = ''; // fill variable with something that won't be matched in first comparison

while ($row = mysql_fetch_assoc($result)) {

    $currentRegionName = $row['RegionName']; // push current region to variable
    if ($currentRegionName != $prevRegionName) echo $row['RegionName'];  // print region only if it changed

    echo "<a href='attraction.php?village=" . $row['AttractionID'] . "'>" .  "<br />" .
          $row['Name']  .
           "<br />" .

          "<img src='" . $row['imglink2'] . "' height='130' width='150'> 

         </a>";


    $prevRegionName = $currentRegionName; // save current region to compare it in next interaction
    }

MySql如何只显示多个表中的数据一次？

4 个答案: