SET @date = NOW();
SET @date = '2017-01-01'; -- Для тестов других годов и месяцев

SET @dayNum = 0;

SELECT
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
@dayNum := @dayNum + 1 c,
id FROM (
    SELECT 1 id UNION
    SELECT 2 UNION
    SELECT 3 UNION
    SELECT 4 UNION
    SELECT 5 UNION
    SELECT 6
) rows_