When you are using GroupBy, which ever columns present in groupBy Clause should be in Select Clause
select MessageGroup,count(MessageGroup)from tblMessage
where SenderId=2
group by MessageGroup
Pergunta
I am asking a very beginner level of question but I am always confused whenever I want to use aggregate function with Group by. Actually I am getting the right results but I am not pretty sure about how group by is working here. My requirement is to get the count of sent items which is based on MessageGroup columns.
MessageId SenderId MessageGroup Message
_____________________________________________________________________________
1 2 67217969-e03d-41ec-863e-659ca26e660f Hi
2 2 67217969-e03d-41ec-863e-659ca26e660f Hello
3 2 67217969-e03d-41ec-863e-659ca26e660f bye
4 1 c45dc414-9320-40a5-8f8f-9c960d6deffe TC
5 1 8486d16b-294b-45a5-8674-e7024e55f39b shutup
Actually I want to get the count for sent messages.here SenderId=2 has sent three messages to someone but I want to show a single count so I have used MessageGroup and I am doing Groupby and getting the count.
I have used Linq query::
return DB.tblMessage.Where(m => m.SenderId == 2 ).GroupBy(m => m.MessageGroup).Count();
This returns "1" which is correct and I want to show (1) in sent messages.
But if I try to query the above in SQL Server, it returns 3
Here is my SQL query:
select count(*)
from tblMessage
where SenderId = 2
group by MessageGroup
The Linq query is right As it returns me one as Microsoft says here
Actually I am confused with Group by. Please clear my point.
Solução
When you are using GroupBy, which ever columns present in groupBy Clause should be in Select Clause
select MessageGroup,count(MessageGroup)from tblMessage
where SenderId=2
group by MessageGroup
Outras dicas
You want to include MessageGroup as part of the select, like this:
select MessageGroup, count(*)
from tblMessage
where SenderId=2
group by MessageGroup