Question

I have this medium-sized query and I am having some problems getting certain fields.

SELECT DISTINCT 
  enc.id, enc.cus_id, enc.createdon, enc.status, 
  enc.segment, enc.currentstep, enc.groupid, enc.fdprotocol, 
  enc_task.linkfile, cus.fname, cus.lname, login.first_name, 
  login.last_name, login.username, login.user_code, fp.protocol 
FROM
  mob_encounters_task enc_task, mob_encounters enc, 
  mob_customer cus, mob_login login, mob_protocol_type fp 
WHERE 
  enc.id=enc_task.encounterid 
AND 
  cus.id=enc_task.cus_id 
AND 
  login.id=enc.createdby 
GROUP BY enc.id

fp.protocol is a string, and on the table fp there are up to 5 or 6 “protocols”.

what I wanted to do is if enc.fdprotocol is empty then fp.protocol should be empty, otherwise get the fp.protocol associated to the fp.id= enc.fdprotocol

Please let me know if this sounds confusing, I have been stuck on this for some time

Answer 1

I find that using the actual JOIN syntax makes queries much more readable and maintainable. In this case you need to use a LEFT JOIN and you have to change your syntax for that:

SELECT enc.id, enc.cus_id, enc.createdon, enc.status, enc.segment, 
enc.currentstep, enc.groupid, enc.fdprotocol, enc_task.linkfile, cus.fname, 
cus.lname, login.first_name, login.last_name, login.username, login.user_code, 
fp.protocol 
    FROM mob_encounters_task enc_task
    JOIN mob_encounters enc ON enc.id=enc_task.encounterid
    JOIN mob_customer cus ON cus.id=enc_task.cus_id
    JOIN mob_login login ON login.id=enc.createdby 
    LEFT JOIN mob_protocol_type fp ON fp.id = enc.fdprotocol

Also I don’t believe you need DISTINCT