When testing sql injection with this command:
I am getting this error:

Microsoft OLE DB Provider for ODBC Drivers error '80040e14'

[Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near the keyword 'UNION'.

/productdisplay.asp, line 36

I have tried adding a quotation mark before UNION, but get another error message on unclosed quotation marks. What I think I should be aiming for is to get the "must have equal expression of target sites" error message. Can anyone help me out?