SQL query

Question

hello!

Problem: I want to select max and min date from the table for every row(GROUPING BY id) then perform date difference operation over it. Afterwards i want to divide that diff with 30 and store in another table. HOW TO DO THAT ?
eX TABLE

Name	Date	ID
A	5/3/14	1
B	6/4/14	2
A	5/4/14	1
C	11/8/14	3
D	6/7/14	4
C	7/7/14	3
D	9/9/14	4

my QUERY
SELECT INSERT INTO <TAB2>
SELECT DATEDIFF/30 AS DIFFFROM
(SELECT MAX(DATE),  MIN(DATE) FROM <TAB1>
GROUP BY ID) ;


but its not working pls suggest how to do date