need to know how to remove duplicate rows from SQL to fetch data from a variety of tables; - sql-server

Question

I need data from a variety of tables and below is the only way I know to do it (I just know the basics). The query below works fine but shows duplicates. I need to know how to remove those.
SELECT DISTINCT
a.int_order_id, a.trans_id, a.wtn,a.isp_id,
d.first_name, d.middle_initial, d.last_name,
d.company_name, d.emaiL,
a.ilec_lob, a.node_type_id, a.cddd,
a.isp_ban, a.tos_version, a.isp_ckt_id,
a.isp_circuit_type, a.atm_vpi, a.atm_vci,
a.frs_dlci, b.order_create_date, b.pon,
b.order_status_id, e.trans_status_id,
e.description, c.STREET_NUMBER,
c.STREET_NUMBER_SUFFIX, c.DIRECTIONAL_ID,
c.street_name, c.thoroughfare_id,
c.street_suffix, c.address_line1, c.address_line2,
c.unit_type_id, c.unit_value, c.city, c.state_id, c.zip
FROM
VZEXTRACT1.vvov_os_ord_dsl A
JOIN
VZEXTRACT1.vvov_os_order_details B ON a.int_order_id = b.int_order_id
JOIN
VZEXTRACT1.vvov_os_ord_address C ON b.int_order_id = c.int_order_id
JOIN
vzextract1.vvov_os_ord_contact D ON c.int_order_id = d.int_order_id
JOIN
VZEXTRACT1.vv0v_trans_status E On b.order_status_id = e.trans_status_id
WHERE
a.isp_id NOT IN (657,500)
AND B.ORDER_CREATE_DATE >= to_date('01-may-15')
AND B.ORDER_CREATE_DATE < to_date('30-JUL-15')

Answer 1

When you want to remove duplicate rows you will have to use
Distinct : It will consider distinct of all selected columns so you will have to find out because of which column you are getting duplicate rows even if you have used distinct
Group by : You can use group by clause to get distinct rows. You can use aggregate function for column causing duplicate rows from point 1 and avoid duplicates.
over(partition by) : you can also use this clause for column causing duplicates. Like you concat values of such column ,
wm_concat(my_col)over(partition by id)