What are some common pitfalls to avoid when querying data from multiple tables in PHP?

One common pitfall to avoid when querying data from multiple tables in PHP is using inefficient JOIN queries that can slow down the performance of your application. To solve this issue, you can use separate queries to retrieve data from each table and then combine the results in your PHP code. 

// Query to retrieve data from the first table
$query1 = "SELECT * FROM table1 WHERE condition = 'value'";
$result1 = mysqli_query($connection, $query1);

// Query to retrieve data from the second table
$query2 = "SELECT * FROM table2 WHERE condition = 'value'";
$result2 = mysqli_query($connection, $query2);

// Combine the results from both queries
$data1 = mysqli_fetch_all($result1, MYSQLI_ASSOC);
$data2 = mysqli_fetch_all($result2, MYSQLI_ASSOC);

// Process the data as needed
foreach ($data1 as $row) {
    // Do something with the data from table1
}

foreach ($data2 as $row) {
    // Do something with the data from table2
}

Keywords

SQL joins data duplication incorrect data retrieval performance bottlenecks SQL injection

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