Output amount of nulls for each column in table

-- Outputs the amount of nulls for each column in a table based on its data
-- Runtime: 2 minutes for 7.5 million rows, YMMV
DECLARE @tableschema NVARCHAR(MAX);
DECLARE @tablename NVARCHAR(MAX);
DECLARE @query NVARCHAR(MAX);

-- Arguments:
USE dbname;
SET @tableschema = 'dbo';
SET @tablename = '';

SET @query = (
    SELECT
        'SELECT DISTINCT '
        + string_agg(
                CAST(
                    FORMATMESSAGE('  (
                        SELECT COUNT(*)
                        FROM %s.%s
                        WHERE %s IS NULL
                        ) AS %s'
                        , table_schema, table_name, column_name, column_name
                    )
                    as nvarchar(max)
                    )
            , ', ')
        + ' FROM ' + table_schema + '.' + table_name
        + ';'
    FROM information_schema.columns
    WHERE TABLE_NAME=@tablename
    AND TABLE_SCHEMA=@tableschema
    GROUP BY table_catalog, table_schema, table_name
)

EXECUTE sp_executesql @query;