Question

Need to perform some logic based on the existence of a record in db. Since this function will be called quite often, I’m wondering if the following can be made more efficient…

Also note that the table is an association table(employee_id and department_id together form a composite primary key), so there will only ever be one record that meets the criteria.

Ex:

<?php

    function checkEmpDptAssoc($employee_id, $department_id)
    {
        $sqlQuery = sprintf("SELECT COUNT(*)
                             FROM  employee_department ed
                             WHERE ed.employee_id = '%d'
                             AND   ed.department_id = '%d'",
                             $employee_id,
                             $department_id);

        $result = mysql_query($sqlQuery);
        $row = mysql_fetch_assoc($result);

        if ((int) $row['COUNT(*)'] > 0) {
            return true;
        } else {
            return false;    
        } 

    }
?> 

Answer 1

EXISTS might be a little quicker since you only need to ensure one exists.

SELECT 1 FROM DUAL
WHERE EXISTS (
    SELECT *
    FROM  employee_department ed
    WHERE ed.employee_id = '%d'
        AND   ed.department_id = '%d'
)