I can write
Select
Sum(Case When Resposta.Tecla = 1 Then 1 Else 0 End) Valor1,
Sum(Case When Resposta.Tecla = 2 Then 1 Else 0 End) Valor2,
Sum(Case When Resposta.Tecla = 3 Then 1 Else 0 End) Valor3,
Sum(Case When Resposta.Tecla = 4 Then 1 Else 0 End) Valor4,
Sum(Case When Resposta.Tecla = 5 Then 1 Else 0 End) Valor5
From Resposta
Or
Select
Count(*)
From Resposta Group By Tecla
I tried this over a large number of rows and it seems like taking the same time.
Anyone can confirm this?
I believe the Group By is better because there are no specific treatments. It can be optimized by the database engine. I think the results may depend on the database engine you use. Maybe the one you are using optimizes the first query anderstanding it is like a group by !
You can try the "explain / explain plan" command to see how the engine is computing your querys but with my Microsoft SQL Server 2008, I just can see a swap between 2 operations ("Compute scalar" and "agregate").
I tried such queries on a database table :
the results are quite differents :
So My choice is "Group By". Another benefit is the query is simplyer to write !