sql select distinct one column code example

Example 1: sql server select rows by distinct column

SELECT a.*
FROM emails a
INNER JOIN 
  (SELECT email,
    MIN(id) as id
  FROM emails 
  GROUP BY email 
) AS b
  ON a.email = b.email 
  AND a.id = b.id;

Example 2: select distinct on 2 columns

SELECT agent_code, ord_amount, cust_code, ord_num
FROM orders 
WHERE agent_code='A002';