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

well '+' is an operator so u need to provide the parameter it requires. '+' operator is an binary operator thus we need to provide two parameters to it with the syntax

 value1+value2

though it may take parameters of many data types by writing '+7' you are only sending a String value "+7" replacing your previous value

so u better use

UPDATE table SET credit = '+7' WHERE id='1'

don't confuse '+' operator with other increment operators