nvarchar（max）减慢存储过程

Question

From yesterday, i'm facing a problem:when i call a stored proc from c#,it lasts >5 in, but when i execute it directly from SSMS (in the server machine) its lasts less than 30 seconds.

I have searched in forums and went trough this great article http://www.sommarskog.se/query-plan-mysteries.html but no result.

The script contained in my proc is retrieving 10 columns among them a column called "article" of type nvarchar(max).

When i remove the article column from my Select ,my proc executes quickly.

To further my logic, i have created a new stored proc retrieving just Primary Key Column and nvarchar(max) column.

I'm reproducing the same behaviour.Here is my new proc=MyNewProc(lasts >5 min when called from c# and 0 Secondes in the server from SSMS)

  CREATE PROCEDURE Student.GetStudents
  AS
  BEGIN
 SET NOCOUNT ON
 -----------------
 SELECT StudentId,Article
 FROM Students
 WHERE Degree=1

 END 

MyNewProc returns just 2500 rows.

Is that normal? How can i improve that.

SELECT SUM(DATALENGTH(Article)) FROM Students WHERE Degree=1 the result is 13885838

Answer 1

You're probably transferring a lot of data over the network. That takes time.

Instead of returning article try returning LEFT(article, 50) to see if its an issue with the volume of data or not.

One thing to note is that SSMS will begin populating the results immediately while a C# application probably will not.

Answer 2

In SSMS, go to the following: Tools -> Options

Then go to Query Execution -> SQL Server -> Advanced

From here, look at what check boxes are checked and if there is something that is checked, SSMS will use this automatically when you execute a sproc from inside of it but when you execute it from C# (or whatever client you're using) it won't be used.

I had this same issue and found out that I needed to include the following line at the top of my sproc and it worked perfectly:

SET ARITHABORT ON;