What are some common mistakes to avoid when writing PHP scripts that involve joining tables in a database?

One common mistake to avoid when joining tables in a database using PHP is not properly specifying the columns to select from each table. This can lead to ambiguous column names and incorrect results. To solve this issue, always prefix column names with the table name or alias when joining tables in a query.

// Incorrect way of joining tables without specifying column names
$query = "SELECT * FROM table1 JOIN table2 ON table1.id = table2.id";

// Correct way of joining tables with specified column names
$query = "SELECT table1.id, table1.name, table2.id, table2.description 
          FROM table1 
          JOIN table2 ON table1.id = table2.id";