Question

This is my temporary table :

CREATE TABLE #tmpRecentTxns(SerialID nvarchar(50) null,TranDate datetime2 null)

select * 
from #tmpRecentTxns 
where #tmpRecentTxns.SerialID NOT IN 
         (SELECT distinct Phone 
          FROM ApplicationVariables 
          WHERE datediff(n, vardatetime, getdate()) <= 300)

Here Phone datatype is nvarchar(10) in database.

Problem : when I am going to select value it is taking too much time.

Please help me out how to remove this problem.

Thanks in advance.

Answer 1

I don’t think the fact your Phone is of type NVARCHAR(10) is the reason for poor performance.

First of all, you should make sure you have an index on the vardatetime column in your ApplicationVariables table (including the Phone column).

CREATE INDEX IX_AppVar_VarDateTime
ON dbo.ApplicationVariables(vardatetime) INCLUDE(Phone)

Second, you should change the query so that this index can be used:

SELECT distinct Phone 
      FROM ApplicationVariables 
      WHERE vardatetime >= DATEADD(MINUTE, -300, GETDATE())

Also: I would recommend to use the MINUTE specifier for DATEDADD or DATEDIFF – much clearer what you’re trying to do.