SQL 案例陈述when

Question

I have a question about SQL case statement. I have a table where 1 account can have multiple web ids(users coming from website) and app id (users coming from app). the account id is unique. I want to identify accounts based on webuser and app users. The case statement written is as follows
(CASE WHEN (webid IS NULL AND appid is not null ) THEN 'App user' WHEN (appid IS NULL and webid is not null ) THEN 'Web user' ELSE 'Web and App user' END)
However the categorisation is not working correctly as it is categorsing 1 account as web user or app user as well as Web and App user. How can I fix this issue?

Answer 1

You seem to want to take the account_id into account as well:

(CASE WHEN AccountId IS NULL THEN NULL
      WHEN webid IS NULL AND appid is not null THEN 'App user'
      WHEN appid IS NULL AND webid is not null THEN 'Web user'
      ELSE 'Web and App user'
 END)