How to create/add a column in an SQL select query based on another column's values?

Question

I want to dynamically add another column hook_name, via an SQL select query, based on a condition.

For example if hook_type = 0, table ho

Answer 1

Use a Standard SQL CASE:

SELECT hook_type, 
   CASE hook_type
      WHEN 0 THEN 'OFFER'
      WHEN 1 THEN 'ACCEPT'
      WHEN 2 THEN 'EXPIRED'
   END AS hook_name,
   COUNT(*) AS number_of_exchange_activities 
FROM `exchange` 
GROUP BY hook_type