使用PHP运行多个Mysql查询

Question

我需要使用PHP运行多个Mysql查询。我有一个网站，并从数据库中提取所有信息

$sql = "SELECT * FROM $table WHERE ID=$escape";
$query = mysql_query($sql) or die(mysql_error());
$rentals = mysql_fetch_assoc($query);

现在，我还有另外两个查询需要运行，分别对应上一步和下一步按钮

$sqlPrev = 'SELECT `id` FROM `table`
        WHERE `id` < '$curId' AND `catId` = '$curCat'
        ORDER BY `id` DESC LIMIT 1;

$sqlNext = 'SELECT `id` FROM `table`
        WHERE `id` > '$curId' AND `catId` = '$curCat'
        ORDER BY `id` ASC LIMIT 1;

当我在PHP MyAdmin中运行它们时，我有正确的代码，但是当我试图通过网站执行它们时，我得到了一个mysql错误！

Answer 1

mysql_query一次只能执行一个查询。

基本上，您只需要对mysql_query进行3次调用。

$sql = "SELECT * FROM $table WHERE ID=$escape";
$query = mysql_query($sql) or die(mysql_error());
$rentals = mysql_fetch_assoc($query);

$sqlPrev = 'SELECT `id` FROM `table`
        WHERE `id` < ' . $curId . ' AND `catId` = ' . $curCat . '
        ORDER BY `id` DESC LIMIT 1';

$sqlNext = 'SELECT `id` FROM `table`
        WHERE `id` > ' . $curId . ' AND `catId` = ' . $curCat . '
        ORDER BY `id` ASC LIMIT 1';

$resultPrev = mysql_query($sqlPrev);
$resultNext = mysql_query($sqlNext);

// todo: check that the above queries executed successfully
// if (!$resultPrev) echo mysql_error();

if (mysql_num_rows($resultPrev)) {
    $prev = mysql_fetch_array($resultPrev);
    $prevId = $prev['id'];
} else {
    $prevId = null; // there is no previous item
}

if (mysql_num_rows($resultNext)) {
    $next = mysql_fetch_array($resultNext);
    $nextId = $next['id'];
} else {
    $nextId = null; // there is no next item
}

Answer 2

问题是“在$sqlPrev和$sqlNext，而不是‘。{$curID}只适用于"”。并且没有结尾“或”。

Answer 3

您可能需要在字符串文字和变量之间添加连接运算符(.)。(这在Perl中是必需的；我在PHP中也是这样做的。)

$sqlPrev = 'SELECT `id` FROM `table`
    WHERE `id` < '.$curId.' AND `catId` = '.$curCat.'
    ORDER BY `id` DESC LIMIT 1';

回显发送到数据库的SQL文本。这将揭示问题所在。