如何在SQL连接中使用Count（*）

Question

I am trying to get row count in SQL Server 2008. I am using join which works perfect, I just want to get the total records because at the moment total records go beyond thousand.

select 
    tablet.Approach.ApproachId,StartDateTime,QuestionId 
from 
    Tablet.Approach
join 
    tablet.DataCapture on tablet.Approach.ApproachId = tablet.DataCapture.ApproachId
where 
    QuestionId = 25

So that I can see the existing result plus 1 extra field which displays total number of rows

Answer 1

You can achieve it like this -

Solution: 1

SELECT tablet.Approach.ApproachId
    ,StartDateTime
    ,QuestionId
    ,COUNT(*) OVER () AS TotalRowCount
FROM Tablet.Approach
JOIN tablet.DataCapture ON tablet.Approach.ApproachId = tablet.DataCapture.ApproachId
WHERE QuestionId = 25

Solution: 2 (Using CTE)

;WITH SourceData
as
(
    SELECT tablet.Approach.ApproachId
    ,StartDateTime
    ,QuestionId
    FROM Tablet.Approach
    JOIN tablet.DataCapture ON tablet.Approach.ApproachId = tablet.DataCapture.ApproachId
    WHERE QuestionId = 25

)
,RecordCnt
AS
(
    SELECT COUNT(ApproachId) AS TotalRowCount
    FROM SourceData
)
Select * from SourceData Cross join RecordCnt

Answer 2

try this

select
 count(*),
 tablet.Approach.ApproachId,StartDateTime,QuestionId 
 from Tablet.Approach
 join tablet.DataCapture
 on tablet.Approach.ApproachId = tablet.DataCapture.ApproachId
 where QuestionId = 25
 group by tablet.Approach.ApproachId,StartDateTime,QuestionId

Answer 3

You can get the total number of records using window functions, in particular count() :

select a.ApproachId, StartDateTime, QuestionId,
       count(*) over () as TotalRows
from Tablet.Approach a join
     tablet.DataCapture dc
     on a.ApproachId = dc.ApproachId
where QuestionId = 25;

I also added table aliases. These make the query easier to write and to read.

Answer 4

 SELECT COUNT(*),tablet.Approach.ApproachId,StartDateTime,QuestionId 
 FROM Tablet.Approach
 JOIN tablet.DataCapture ON tablet.Approach.ApproachId = tablet.DataCapture.ApproachId
 WHERE QuestionId = 25
 GROUP BY tablet.Approach.ApproachId,StartDateTime,QuestionId