如何在 PHP 中有效率地執行多個 MySQL 查詢？

使用 MySQL 在 PHP 中執行多個查詢

考慮一個場景，您需要在單一 PHP 腳本中執行多個 SQL 查詢。一種常見的方法是使用 mysqli_multi_query() 函數，它允許您將多個查詢連接到一個字串中。

以下是如何實現此目的的範例：

// 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，如果您希望單獨執行每個查詢，可以使用mysqli_query() 函數多個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'];
}

選擇透過mysqli_multi_query() 將多個查詢連接成單一字串還是透過mysqli_query() 單獨執行它們取決於您的特定要求和效能考慮。

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