Simple Merging A Few Queries In One Query Question

how can I fill a data set with a multi parameter filter:

I want to create in my form few textboxes and create a query that filters the dataset to show only the specific data.
but the problem is if the user doesn't supply any words in some textbox the dataset is not filled.

it would be a good solution for me if I can either:
for example let's say my query is SELECT * FROM table WHERE column = @parameter,
i want to write before the query something like "if @parameter="" then replace the query syntax near WHERE with * so it looks SELECT * FROM table WHERE column = *.
or:
if there is some character or character series that sql reconizes in a parameter as an asterisk.

thank you for your time!