SELECT COUNT(DISTINCT… ) error on multiple columns?

Question

I have a table, VehicleModelYear, containing columns id, year, make, and model.

The following two queries work as expected:

SELECT DISTINCT make, model
F         


        

Answer 1

COUNT() in SQL Server accepts the following syntax

COUNT(*)
COUNT(colName)
COUNT(DISTINCT colName)

You can have a subquery which returns unique set of make and model that you can count with.

SELECT  COUNT(*)
FROM
        (
            SELECT  DISTINCT make, model
            FROM    VehicleModelYear
        ) a

The "a" at the end is not a typo. It's an alias without which SQL will give an error ERROR 1248 (42000): Every derived table must have its own alias.