Is there a gain in efficiency if I put a lengthy SQL select into a stored procedure? - sql-server

Question

I have the following SQL Server 2012 query:
var sql = #"Select question.QuestionUId
FROM Objective,
ObjectiveDetail,
ObjectiveTopic,
Problem,
Question
where objective.examId = 1
and objective.objectiveId = objectiveDetail.objectiveId
and objectiveDetail.ObjectiveDetailId = ObjectiveTopic.ObjectiveDetailId
and objectiveTopic.SubTopicId = Problem.SubTopicId
and problem.ProblemId = question.ProblemId";
var a = db.Database.SqlQuery<string>(sql).ToList();
Can someone help explain to me if it would be a good idea to put this into a
stored procedure and if so then how could I do that and then call it from my C# code. It was
suggested to me that if it is in a stored procedure then it would run more
efficiently as it would not be recompiled often. Is that the case?

Answer 1

Yes, there is. For starters, a stored procedure is precompiled and stored within your database. Being precompiled, the database engine can execute it more efficiently, since no on-the-fly compilation necessary. Also, database optimizations can be added to support a precompiled procedure. A stored procedure also allows business logic to be encapsulated within the database.
If you decide to go the stored procedure route, then consider the following:
First of all, you will need to create a stored procedure that encapsulates your existing SQL query.
CREATE PROCEDURE ListQuestionIds
#ExamId int
AS
BEGIN
SELECT Question.QuestionUId
FROM Objective
INNER JOIN ObjectiveDetail
ON ( Objective.objectiveId = ObjectiveDetail.objectiveId )
INNER JOIN ObjectiveTopic
ON ( ObjectiveDetail.ObjectiveDetailId = ObjectiveTopic.ObjectiveDetailId )
INNER JOIN Problem
ON ( ObjectiveTopic.SubTopicId = Problem.SubTopicId )
INNER JOIN Question
ON ( Problem.ProblemId = Question.ProblemId )
WHERE Objective.examId = #ExamId;
END;
Please make sure that the tables called by your procedure (Objective, Problem, etc,) have all of the relevant primary keys and indexes in place to enhance the performance of your query.
Next, you will need to call that stored procedure from within your C# code. One way--but by no means the only way--is to create a connection to your database using the SqlConnection object and then executing your procedure via the SqlCommand object.
I would recommend that you take a look at How to execute a stored procedure within C# program for some on-topic examples. But a simple example of such might look like:
string connectionString = "your_connection_string";
using (var con = new SqlConnection(connectionString))
{
using (var cmd = new SqlCommand("ListQuestionIds", con)) {
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.Add(new SqlParameter("#ExamId", examId))
con.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
// Loop through the returned SqlDataReader object (aka. rdr) and
// then evaluate & process the returned question id value(s) here
}
}
}
}
Please note that this sample code does not (intentionally) include any error handling. I leave that up to you to integrate into your application.
Finally, just as an FYI... many of the more modern ORMs (e.g., Entity Framework, NHibernate, etc.) allow you to execute stored procedure-like queries from your C# code without requiring an explicit stored procedure. If you are already using an ORM in your application, then you may want to forgo the stored procedure altogether. Whatever you decide to do, a little research on your end will help you make an informed decision.
I hope this helps you get started. Good luck.