What are the potential pitfalls when trying to add up a variable number of rows in a MySQL table using PHP?

When trying to add up a variable number of rows in a MySQL table using PHP, the potential pitfalls include not properly handling errors or empty result sets, not sanitizing user input to prevent SQL injection, and not properly iterating through the result set to calculate the sum accurately. To solve this issue, you should check for errors after executing the query, sanitize user input using prepared statements, and use a loop to iterate through the result set and calculate the sum. 

// Connect to MySQL database
$mysqli = new mysqli("localhost", "username", "password", "database");

// Check connection
if ($mysqli->connect_error) {
    die("Connection failed: " . $mysqli->connect_error);
}

// Prepare and execute query
$query = "SELECT column_name FROM table_name WHERE condition";
$result = $mysqli->query($query);

// Check for errors
if (!$result) {
    die("Error in query: " . $mysqli->error);
}

// Initialize sum variable
$sum = 0;

// Iterate through result set and calculate sum
while ($row = $result->fetch_assoc()) {
    $sum += $row['column_name'];
}

// Output sum
echo "The total sum is: " . $sum;

// Close connection
$mysqli->close();

Keywords

MySQL PHP SUM function dynamic rows data manipulation

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