Is there any way in Tableau to use variables from an Oracle query? I'd like to specify the variable and then input a value to substitute into the query _before_ pulling data, in order to make my connections feasible. So if I'm pulling data over the last &&numdays, I would like to use that variable in the connection and then set values when updating the connection, as appropriate. Thanks for any help!
To my knowledge this is not yet possible (as of v 7.0).
Depending on what you want to accomplish, you might try using Tableau internal filter/extract functionality, i.e. connect to all data, but only extract what you need (will involve a manual step of changing the filter and refreshing extract).
There is also the RAW_SQL pass-through functions, but I don't think they would be applicable in this case.