How do I fix my code so it runs correctly, it keeps telling me I have Error Code 1055-CodePudding

Trying to complete this multi-query assignment but cannot figure out why I keep getting this error code (Error Code: 1055. Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'ebe.Co.ContactName' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by). This is my code below

USE EBE;

SELECT C.ClientName, CO.ContactName, CO.ContactPhone, CO.ContactEmail,
  COUNT(E.EventCode) AS NumberOfEvents
FROM Client AS C 
INNER JOIN Contact AS CO ON C.ClientID = CO.ClientID 
INNER JOIN Events AS E ON C.ClientID = E.ClientID
GROUP BY E.ClientID
ORDER BY C.ClientName;

CodePudding user response：

All the columns that are being selected except for the aggregated column need to be in the GROUP BY

SELECT C.ClientName, CO.ContactName, CO.ContactPhone, CO.ContactEmail, 
    COUNT(E.EventCode) AS NumberOfEvents 
FROM Client AS C 
INNER JOIN Contact AS CO ON C.ClientID = CO.ClientID 
INNER JOIN Events AS E ON C.ClientID = E.ClientID 
GROUP BY C.ClientName, CO.ContactName, CO.ContactPhone, CO.ContactEmail
ORDER BY C.ClientName

CodePudding user response：

Another way of writing your query to remove the need for group by would be to use a correlated subquery:

select C.ClientName,
  CO.ContactName, 
  CO.ContactPhone,
  CO.ContactEmail,
  (select Count(*) from Events E where E.ClientID = C.ClientID) NumberOfEvents
from Client C
join Contact CO on CO.ClientID = c.ClientID
order by C.ClientName;