What are some common pitfalls when working with multiple tables and querying data in PHP?

One common pitfall when working with multiple tables and querying data in PHP is not properly joining the tables together in the SQL query. This can result in incomplete or incorrect data being returned. To solve this issue, make sure to correctly specify the join conditions between the tables to ensure that the data is properly linked. 

// Example of joining two tables in a SQL query
$query = "SELECT table1.column1, table2.column2 
          FROM table1 
          JOIN table2 ON table1.id = table2.table1_id";
$result = mysqli_query($connection, $query);

// Process the query result
if(mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        // Process each row of data
    }
}

Keywords

SQL joins data normalization foreign keys PDO SQL injection

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