How to stop a running query?

Question

I use RODBC to send queries to an SQL-Server. Sometimes they take too much time to run, so I need to cancel them.

Clicking the red \"stop\" button in RStudio yields this

Answer 1

try to set your connection prior to query:

sql = odbcConnect('Database name')

Then use same line to run your query:

mydf <- sqlQuery(sql, " myquery ")

Note: The running time is dependant on both database and R server but setting up the connection this way should resolve termination problem.

Answer 2

I've just stumbled upon the odbc package. It allows to interrupt a query at any time.

Basic usage goes like this:

library(DBI)

myconnection <- dbConnect(odbc::odbc(),
                          driver = "SQL Server",
                          server = "my_server_IP_address",
                          database = "my_DB_name",
                          uid = "my_user_id",
                          pwd = "my_password")

dbGetQuery(myconnection, myquery)

I don't have a deep understanding of what happens behind the scenes, but for what I've seen so far in my personal use this package has other advantages over RODBC:

• really faster
• get the column types from the DB instead of guessing them (see here)
• no stringsAsFactors and as.is arguments necessary

Answer 3

Try to close your "tab query" on SQL Server Management Studio Then it will appear pop-up,

This Query is currently executing. Do you want to cancel this query ?

Cancel anyway, choose "yes".

Answer 4

Most SQL Server users use SQL Server Management Studio (which is free and can be downloaded from Microsoft) to connect to SQL Server or execute commands from the command line via a tool called SQLCMD.

If you can determine the session id that the SQL Command is being run in you can kill the session which would stop any executing command(s). SQL Server will still need time (could be a 'long' time) to rollback any changes made during the execution of the command.

Terminating a session (depending on the software) can take a while to communicate to SQL Server that the session has been terminated. When I connected to DB2 from SQL Server using linked servers DB2 would buffer the terminate command and it would frequently take up to an hour for DB2 to realize the session had been terminated.

To determine what the session you are running in you can try:

select @@spid;

once you have the spid (lets say 86) you can then issue (depending on if you have permission to do so)

kill 86;

but as Microsoft notes: Terminates a user process that is based on the session ID or unit of work (UOW). If the specified session ID or UOW has a lot of work to undo, the KILL statement may take some time to complete, particularly when it involves rolling back a long transaction.