/ Character in a stored procedure
Your outer select is incomplete, it has no FROM clause.

Once that's fixed your query may work, if not try putting each of the sub selects inside of a pair of parenthesis, and possibly the whole operation.

Insert Into Production(A, B, C)      
SELECT A
     , B
     , ( (SELECT SUM(Month_Production) FROM Production)
       / (SELECT COUNT(Month_Production) FROM Production)
       ) C
  from some_table;  -- &lt;== This is missing


By the way since both the numerator and the denominator are coming from the same table, this would be a more efficient query:

SELECT A
     , B
     , (SELECT SUM(Month_Production) 
             / COUNT(Month_Production)
          FROM Production
       ) C
  from some_table;


Since it only has to access the whole Production table once instead of twice