How to use union query on the same table and sum (value) in mysql?

Question

I have a table :

OC  Period(MM/YYYY) Ing
CHO 04/01/2016      100
CHO 04/01/2016      200
CHO 04/01/2016      0
CFE 04/01/2016      400
CFE 04/01/2016      350
CFE 04/01/2016      0

I have an SQL query like this:

  (SELECT OC,Ing FROM contacts c where ing > 0)
  UNION ALL
  (SELECT OC,Sum(Ing) FROM contacts c where ing = 0 Group by OC)

I want to get a result like this:

Ref Period(MM/YYYY) Ing
CHO 04/01/2016      100
CHO 04/01/2016      200
CHO 04/01/2016      300
CFE 04/01/2016      400
CFE 04/01/2016      350
CFE 04/01/2016      750

Answer 1

(SELECT c.OC, c.Period, c.Ing FROM contacts c where c.ing > 0)
UNION ALL
(SELECT c.OC, c.Period, Sum(c.Ing) AS Ing FROM contacts c Group by c.OC, c.Period)

You could wrap it in another select from statement if you need to sort the output