Hello,

The SQLDataSource web part does not provide any property that you can use to specify query parameters.
You will need to create a custom web part that will be based on SQLDataSource control and define query parameters from code:

You can use the QueryParameters property of the SQLDataSource:

object[,] parameters = new object[1, 3];

parameters[0, 0] = "@FieldName";
parameters[0, 1] = FieldName;

SQLDataSource.QueryParameters = parameters;

If you need more information about developing a web part, I would like to point you to the following article: Developing web parts.

Best regards,
Michal Legen