I feel the problem lies the way in which the case function has been implemente. There are 2 ways of implementing the case statement, simple case and searched case. Not...

May be I am shooting arrows in the dark, but my feleing here is that the query has become slow due to defragmentation of data.

Try using dbcc showcontig command.

For more...

One more way is to replace all single instance of "'" with "''" using replace function.

Select ControlID from SendController

Group By ControlID,Datetime

having count(controlid) <10

One assumtion here is the datetime table does not have time embedded in them.

You Can always pass the string as using Connection.execute method or us command object to do the same. This can be done after the connection is successfully opened.