In what scenarios would it be advisable to use CASE statements in SELECT queries in PHP, and how can they improve query performance and readability?

Using CASE statements in SELECT queries in PHP can be useful when you need to conditionally return different values based on certain criteria. This can improve query performance by reducing the number of queries needed to retrieve the desired data. Additionally, CASE statements can enhance readability by making the logic more explicit and easier to understand. 

$query = "SELECT 
            id, 
            name, 
            CASE 
                WHEN age < 18 THEN 'Minor' 
                WHEN age >= 18 AND age < 65 THEN 'Adult' 
                ELSE 'Senior' 
            END AS age_group 
          FROM users";

$result = mysqli_query($connection, $query);

if(mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        echo "ID: " . $row['id'] . ", Name: " . $row['name'] . ", Age Group: " . $row['age_group'] . "<br>";
    }
} else {
    echo "No results found.";
}

Keywords

PHP CASE statement SELECT query query performance readability

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