What are some best practices for handling duplicate data entries or conflicting values when merging data from multiple tables in a database query using PHP and SQL?

When merging data from multiple tables in a database query using PHP and SQL, it is important to handle duplicate data entries or conflicting values to ensure data integrity. One common approach is to use SQL functions like DISTINCT or GROUP BY to eliminate duplicates. Another approach is to prioritize certain tables or columns over others when merging conflicting values. Additionally, using conditional statements in PHP to compare and resolve conflicting values can help maintain data consistency. 

// Example code snippet to handle duplicate data entries or conflicting values when merging data from multiple tables in a database query

// Assuming $conn is the database connection object

// Query to merge data from multiple tables and handle duplicates or conflicts
$sql = "SELECT DISTINCT column1, column2, column3 FROM table1
        UNION
        SELECT column1, column2, column3 FROM table2
        ORDER BY column1";

$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Output data of each row
    while($row = $result->fetch_assoc()) {
        echo "Column1: " . $row["column1"]. " - Column2: " . $row["column2"]. " - Column3: " . $row["column3"]. "<br>";
    }
} else {
    echo "0 results";
}

Keywords

SQL PHP database query duplicate data conflicting values

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