How to select data from 30 days?
Solution 1:
You should be using DATEADD is Sql server so if try this simple select you will see the affect
Select DATEADD(Month, -1, getdate())
Result
2013-04-20 14:08:07.177
in your case try this query
SELECT name
FROM (
SELECT name FROM
Hist_answer
WHERE id_city='34324' AND datetime >= DATEADD(month,-1,GETDATE())
UNION ALL
SELECT name FROM
Hist_internet
WHERE id_city='34324' AND datetime >= DATEADD(month,-1,GETDATE())
) x
GROUP BY name ORDER BY name
Solution 2:
Try this : Using this you can select date by last 30 days,
SELECT DATEADD(DAY,-30,GETDATE())