Please, read my comment first.
If you want to fetch only unique values, please, try this:
DECLARE @tmp TABLE (MyNumber INT)
INSERT INTO @tmp (MyNumber)
SELECT 590
UNION ALL SELECT 800
UNION ALL SELECT 800
UNION ALL SELECT 289
UNION ALL SELECT 800
UNION ALL SELECT 590
UNION ALL SELECT 478
UNION ALL SELECT 123
UNION ALL SELECT 800
UNION ALL SELECT 600
SELECT DISTINCT MyNumber
FROM @tmp
SELECT MyNumber, COUNT(MyNumber) AS CountOfMyNumber
FROM @tmp
GROUP BY MyNumber
Frist query result set:
MyNumber
123
289
478
590
600
800
Second query result set:
MyNumber CountOfMyNumber
123 1
289 1
478 1
590 2
600 1
800 4