如何在 PHP 中高效运行多个 MySQL 查询？

使用 MySQL 在 PHP 中运行多个查询

考虑一个场景，您需要在单个 PHP 脚本中执行多个 SQL 查询。一种常见的方法是使用 mysqli_multi_query() 函数，它允许您将多个查询连接到一个字符串中。

以下是如何实现此目的的示例：

// Create database connection
$conn = mysqli_connect('server', 'user', 'password', 'database');

// Construct the multiple queries as a single string
$query = "CREATE VIEW current_rankings AS SELECT * FROM main_table WHERE date = X;";
$query .= "CREATE VIEW previous_rankings AS SELECT rank FROM main_table WHERE date = date_sub('X', INTERVAL 1 MONTH);";
$query .= "CREATE VIEW final_output AS SELECT current_rankings.player, current_rankings.rank as current_rank LEFT JOIN previous_rankings.rank as prev_rank ON (current_rankings.player = previous_rankings.player);";
$query .= "SELECT *, @rank_change = prev_rank - current_rank as rank_change from final_output;";

// Execute the multiple queries
if (mysqli_multi_query($conn, $query)) {
    // Process each result set
    do {
        // Check for the first result set
        if ($result = mysqli_store_result($conn)) {
            // Fetch and display the results
            while ($row = mysqli_fetch_array($result)) {
                echo $row['player'] . ' ' . $row['current_rank'] . ' ' . $row['prev_rank'] . ' ' . $row['rank_change'];
            }
            // Free the result set
            mysqli_free_result($result);
        }
    } while (mysqli_next_result($conn));
} else {
    // Handle any errors
    echo mysqli_error($conn);
}

或者，如果您希望单独执行每个查询，可以使用 mysqli_query() 函数多个times:

// Create temporary table A
$query1 = "Create temporary table A select c1 from t1";
mysqli_query($conn, $query1) or die(mysqli_error($conn));

// Select from temporary table A
$query2 = "select c1 from A";
$result2 = mysqli_query($conn, $query2) or die(mysqli_error($conn));

// Fetch and display the results
while ($row = mysqli_fetch_array($result2)) {
    echo $row['c1'];
}

选择通过 mysqli_multi_query() 将多个查询连接成单个字符串还是通过 mysqli_query() 单独执行它们取决于您的具体要求和性能考虑。

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