retrieve unique values from database code example

Example 1: DISTINCT SQL

SELECT DISTINCT column1, column1, ..... FROM TABLE
/*DISTINCT WILL NOT SELECT THE SAME VALUES IN SAME COLUMN*/

Example 2: 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;