Conditionally Extend Query With Clauses

Howdy folks, first time poster.

In a UDF, how is the best way to extend a query with additional clauses based on expressions? The user input here is used to refine the basic query by introducing additional clauses. Is there something like the following?


-- The basic query
SELECT column
FROM table
WHERE clause

-- Additional clause, only appended to query
-- if expression evaluates to true
IF @parameter <> default_value
BEGIN
AND additional_clause
END


Right now I'm using CASE like the following, but it necessarily makes the query longer. Is there a more efficient way?


-- The basic query

SELECT column
FROM table
WHERE clause

-- Additional clause, should only effect result
-- set when the parameter is not default_value
AND table.column =
CASE @parameter
WHEN default_value THEN
-- identity, table.column=table.column,
-- should have no effect other than just a long query
table.column
ELSE
@parameter
END