How to organize SQL select functions? - php

Question

I want to get information by user id, so lets add this to the model:
public function getById ($id)
{
$sql = 'SELECT * FROM users';
return ActualDbHander::run($sql);
}
later, I want to get only some fields:
public function getById ($id, $fields = '*')
{
$sql = 'SELECT '.$fields.' FROM users';
return ActualDbHander::run($sql);
}
another idea, lets add ordering:
public function getById ($id, $fields = '*', $orderBy = '')
{
$sql = 'SELECT '.$fields.' FROM users';
if ($orderBy != '')
{
$sql.= ' ORDER BY '.$orderBy;
}
return ActualDbHander::run($sql);
}
and I see this becaming messy and messy. What if I want to add JOIN-s? What if I want to add detailed WHERE-s? This is when "too generalic" methods born.

Answer 1

I completely agree with mch and Mjh comments, but, only in the case you actually want to have a "BD driver" (and build it yourself) I'd use different names for each query, very specific names, because you need to know exactly what a function will return to you.
So if I were you I would use names like getAllUsers, getUserById, getAllUsersOnlyPersonalData, getUserByIdOnlyPersonalData, getAllUsersOnlyContactData and so on (with fixed fields and filters for each method).
Note that in your examples you are not using at all the $id variable, so you are always receiving a list of users.
Regarding the method to make the queries, there are lots of ways to do it. Personally, I prefer MySQLi Object-Oriented prepared statements, because it's safe, easy and currently very extended, so I will use it just to ilustrate the examples.
Your functions would be something like this:
<?php
class DBDriver{
function openConnection(){
// If you don't always use same credentials, pass them by params
$servername = "localhost";
$username = "username";
$password = "password";
$database = "database";
// Create connection
$conn = new mysqli($servername, $username, $password, $database);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
// Return conection object
return $conn;
}
function closeConnection($conn){
$conn->close();
}
function getAllUsers (){ // We don't need ids here
$conn = $this->openConnection();
// Array of arrays to store the results
// You can use any other method you want to return them
$resultsArray = [];
$sqlQuery = "SELECT * FROM users";
// In this case it's not neccesary to use prepared statements because we aren't binding any param but we'll use it to unify the method
if ($stmt = $conn->prepare($sqlQuery)) {
// Execute query
$stmt->execute();
// Bind result variables (I don't know your actuall column names)
$stmt->bind_result($id, $name, $email, $phone, $birthdate);
// Fetch values
while ($stmt->fetch()) {
$resultsArray[] = [$id, $name, $email, $phone, $birthdate];
}
// Close statement
$stmt->close();
}
$this->closeConnection($conn);
// If no results, it returns an empty array
return $resultsArray;
}
function getUserByIdOnlyContactData ($userId){
$conn = $this->openConnection();
// Array to store the results (only one row in this case)
$resultsArray = [];
$sqlQuery = "SELECT name, email, phone FROM users WHERE id = ?";
if ($stmt = $conn->prepare($sqlQuery)) {
// Bind parameter $userId to "?" marker in $sqlQuery
$stmt->bind_param("i", $userId);
$stmt->execute();
$stmt->bind_result($name, $email, $phone);
// If id found
if ($stmt->fetch()) {
$resultsArray = [$name, $email, $phone];
}
// Close statement
$stmt->close();
}
$this->closeConnection($conn);
return $resultsArray;
}
function getAllUserOnlyBirthdayDataOrderByBirthday (){
$conn = $this->openConnection();
$resultsArray = [];
$sqlQuery = "SELECT id, name, birthdate FROM users ORDER BY birthdate";
if ($stmt = $conn->prepare($sqlQuery)) {
$stmt->execute();
$stmt->bind_result($id, $name, $birthdate);
while ($stmt->fetch()) {
$resultsArray[] = [$id, $name, $birthdate];
}
// Close statement
$stmt->close();
}
$this->closeConnection($conn);
return $resultsArray;
}
} // Class end
This way it's true you will have lots of functions depending on your requirements but as you can see it's extremely easy to add new ones or modify them (and you won't get mad with many different options in the same function).
Hope this helps you to organize your database driver!