How to Execute Multiple MySQL Queries Efficiently in PHP?

MySQL Multiple Queries in PHP

When dealing with complex database operations, executing multiple queries in a single PHP script can be necessary. Here's how to achieve it using PHP and MySQL:

In your case, you were encountering errors while attempting to merge multiple queries into a single result. To resolve this, the key solution is to utilize mysqli_multi_query() function. By concatenating your queries and passing them to this function, you can execute them sequentially.

Here's a revised version of your code using mysqli_multi_query():

$link = mysqli_connect("server", "user", "password", "database");

$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, previous_rankings.rank AS prev_rank FROM current_rankings LEFT JOIN previous_rankings ON (current_rankings.player = previous_rankings.player);";
$query .= "SELECT *, @rank_change = prev_rank - current_rank AS rank_change FROM final_output;";

if (mysqli_multi_query($link, $query)) {
    do {
        if ($result = mysqli_store_result($link)) {
            while ($row = mysqli_fetch_array($result)) {
                echo $row['player'] . ' ' . $row['current_rank'] . ' ' . $row['prev_rank'] . ' ' . $row['rank_change'] . '<br>';
            }
            mysqli_free_result($result);
        }
    } while (mysqli_next_result($link));
}

Remember to replace "X" in the queries with the appropriate date parameter.

Alternative Approach

If executing queries sequentially is sufficient, you can use multiple mysqli_query() calls to execute each query individually. For example:

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

$query2 = "select c1 from A;";
$result2 = mysqli_query($link, $query2) or die(mysqli_error());

while ($row = mysqli_fetch_array($result2)) {
    echo $row['c1'];
}

The above is the detailed content of How to Execute Multiple MySQL Queries Efficiently in PHP?. For more information, please follow other related articles on the PHP Chinese website!