PHP / SQL：框架查询构建vs字符串连接

Question

Consider 2 ways of querying the database:

With a framework (Yii):

$user = Yii::app()->db->createCommand()
->select('id, username, profile')
->from('tbl_user u')
->join('tbl_profile p', 'u.id=p.user_id')
->where('id=:id', array(':id'=>$id))
->queryRow();

With string concatenation (separating individual parts of a SQL statement):

$columns = "id,username,profile"; // or =implode(",",$column_array);
//you can always use string functions to wrap quotes around each columns/tables
$join = "INNER JOIN tbl_profile p ON u.id=p.user_id";
$restraint = "WHERE id=$id ";//$id cleaned with intval()
$query="SELECT $columns FROM tbl_user u {$restraint}{$join}";
//use PDO to execute query... and loop through records...

Example with string concatenation for pagination:

$records_per_page=20;
$offset = 0;
if (isset($_GET['p'])) $offset = intval($_GET['p'])*$records_per_page;
Squery="SELECT * FROM table LIMIT $offset,$records_per_page";

Which method has better performance?

• PHP's PDO allows code to be portable to different databases
• 2nd method can be wrapped in a function so no code is ever repeated.
• String concatenation allows building complex SQL statements programmatically (by manipulating strings)

Answer 1

Use which is right for you and your project team. Frameworks are written for a reason, so use them if it suits, but if it doesn't (and there are reasons they don't) then fall away.

I don't know Yii, but if you look at a lot of frameworks, all they do is build a string query from the parts at the end of the day, hopefully taking advantage of parametization but not always. So, regarding speed, string concat is probably "fastest" - but you're unlikely to really see the difference with a stop watch (you could benchmark if you needed with 1000 queries, but other features such as better error checking or caching may unfairly slow or speed up hte results).

But one advantage frameworks have is they can add context-sensitive caching and know when you update table X that you query caches for A, D and F need to be deleted, but queries B, C and E are all good.

You also have "easy to read" and "debug" and "functionality" to worry about. The top example is much easier to read, which is important in a shared project.

You also need to consider prepared statements - does the framework use them? If so, does it allow you to re-use them (as opposed to merely using them for syntax purposes).

But can the framework do sub-selects? Can it do parametization inside the "JOIN ON"? If not, string concatination with PDO may be more appropriate.

It's not a hard and fast answer - but hopefully provides all the points you need to consider.

Recommendation: use framework unless you really notice it being slow, using too much memory or there is some other good reason not to.