Question

New to SQL and I’ve just created a SQL query with assitance:

       SELECT CASE

    WHEN exists (SELECT CLIENT_CODE FROM STG_DM_CLIENT      
       WHERE CLIENT_CODE 
      NOT IN (SELECT CLIENT_CODE FROM DM_CLIENT)) THEN 'A'
      else

WHEN  exists (SELECT STG.CLIENT_CODE AS TRAN_TYPE
    FROM  STG_DM_CLIENT STG          
    JOIN DM_CLIENT SRC
    ON SRC.CLIENT_CODE = STG.CLIENT_CODE  
    WHERE (SRC.CLIENT_NAME <> STG.CLIENT_NAME)) THEN 'C'
    END 
FROM DM_CLIENT, STG_DM_CLIENT

Fails to provide the correct resulset, states incorect syntax next to when

Msg 156, Level 15, State 1, Line 8
Incorrect syntax near the keyword ‘WHEN’.

Any ideas as to what I’m doing wrong

Answer 1

It’s not clear what your after, this is the closest valid statement;

SELECT 
    CASE WHEN EXISTS (...) 
        THEN 'A'
    ELSE 
        CASE WHEN EXISTS (...) 
            THEN 'C'
            ELSE 'Neither exists()'
        END
    END

When the 1st exists is matched you will get A
When the 1st does not exist you will get C if the 2nd does match