How can SQL queries be optimized to prevent returning duplicate data in PHP applications?

To prevent returning duplicate data in PHP applications when querying a database using SQL, you can use the DISTINCT keyword in your SELECT statement to ensure only unique rows are returned. Additionally, you can use GROUP BY to group the results by a specific column to avoid duplicates. Another way to prevent duplicates is to carefully design your database schema to avoid redundant data. 

$query = "SELECT DISTINCT column1, column2 FROM table_name";
$result = mysqli_query($connection, $query);

if(mysqli_num_rows($result) > 0){
    while($row = mysqli_fetch_assoc($result)){
        // Process each unique row here
    }
}

Keywords

SQL queries optimization duplicate data PHP applications performance.

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