If i understand you correctly... you need to change your query as follow:
select [ID],[question],[answer],
COUNT(CASE WHEN [answer] LIKE'%coca-cola%' THEN 1 ELSE NULL END) existing_customer
,COUNT(CASE WHEN NOT [answer] LIKE'%coca-cola%' THEN 1 ELSE NULL END) potential_customer
group by id,question, answer
Why?
MSDN wrote:
COUNT(*)
returns the number of items in a group. This includes NULL values and duplicates.
COUNT(ALL expression)
evaluates expression for each row in a group, and returns the number of nonnull values.
COUNT(DISTINCT expression)
evaluates expression for each row in a group, and returns the number of unique, nonnull values.
Source:
COUNT (Transact-SQL) - SQL Server | Microsoft Docs[
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