Help with queries.

Dear group,

I just started learning postgres and I have to analyze my data.  So
please bear with me, for all the simple questions that I am asking.
Apologies.


I have a table:

snps table

id   |   sample_id | chromosome | from  | to |
----------------------------------------------------------------
1         1                chr1             10       11
2          1              chr1               14       15
3          2              chr1               14       15
4         2               chr1                9         10
5         3              chr1                14        15
6          3             chr14              35        36
7          3             chr14              39        40
8          2             chr14              39        40
9          2             chr14              43        44
10        1             chr14              43        44


gene table:

id |   chromosome | from | to  | genename
1         chr1            4       20    SRC
2         chr1           25      45    SRC
3         chr1           80      100   CSK
4         chr1          120     140   CSK

My aim is to for a gene in gene table (SRC that has two ranges 4-20 and 25-45),
I want to map all coordinates in snps table.
Then I want to get those entries where sample 1 and sample 2 have in
common and sample 1 and sampl3 in common.


I do not know how to get these entries. Could any one help me please.

thank you.

adrian