I'm not sure if it matters, but I think there should be a space between -s
and ","
But more importantly, your pipe construct is wrong. Your sqlcmd command is running in a new window, but your pipe is looking for output from the START command itself in the original window - and there isn't any.
You could get your command to work by escaping the pipe and redirection.
@echo off
cd C:\Program Files (x86)\Microsoft SQL Server\Client SDK\ODBC\110\Tools\Binn\
start /w "sqlcmd" sqlcmd.exe -S DBserverName -U username -P p@ssword -i "C:\query.sql" -s "," ^| findstr /V /C:"-" /B ^>"c:\output.csv"
But there is no need to use START at all. Your script can simply execute sqlcmd directly, and everything is much simpler.
@echo off
cd C:\Program Files (x86)\Microsoft SQL Server\Client SDK\ODBC\110\Tools\Binn\
sqlcmd.exe -S DBserverName -U username -P p@ssword -i "C:\query.sql" -s "," | findstr /V /C:"-" /B >"c:\output.csv"
You might also be running into problems with your password, depending on what characters are used. You might have to quote and/or escape the password, and sqlcmd.exe might have its own escape rules. If it does, then you might have to worry about escaping for both cmd.exe and sqlcmd.exe.