SQL Select Expression Substitution

I have a number of links with a length of 20 and I need to remove the 1st 12 numbers, replace with G and select the next 7 numbers

An example of the format of accepted numbers

50125426598525412584

      

        
        
        
      

    

Then I need to remove the first 12 digits and select the next 7 (not including the last)

2541258

      

        
        
        
      

    

Finally, I need to put a G in front of the number so that I stay with

G25412584

      

        
        
        
      

    

My SQL looks like this:

SELECT SUBSTRING(ref, 12, 7) AS ref 
FROM mytable
WHERE ref LIKE '5012%'

      

        
        
        
      

    

The results of this will leave me with

25412584

      

        
        
        
      

    

But how do you insert G

before the number in the same SQL statement?

Many thanks