In the context of PHP database queries, when would it be more appropriate to use a left join versus an equi join?

When you want to retrieve all records from the left table (the table mentioned first in the query) regardless of whether there is a matching record in the right table, you should use a left join. This is useful when you want to include all records from the left table even if there are no corresponding records in the right table. On the other hand, an equi join is used when you want to retrieve only the records that have matching values in both tables. 

$query = "SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.id";
$result = mysqli_query($connection, $query);

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

Keywords

PHP database queries left join equi join SQL

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