How to update field to add value to existing value?

Question

How to update field to add value to existing value?
For example I have

Table name: table

id   credit
1      4
2      5
3      3
         


        

Answer 1

I wanted to add to this with an 'ON DUPLICATE KEY UPDATE' example(based on the answer by @hims056). I found this answer but needed 'ON DUP...' so I figured may as well post it here.

INSERT INTO table1 
(`id`, `credit`)
VALUES (1, 4)
ON DUPLICATE KEY UPDATE
`credit` = `credit` + 7;

See the SQL Fiddle here