Count number of records returned by group by

Question

How do I count the number of records returned by a group by query,

For eg:

select count(*) 
from temptable
group by column_1, column_2, column_3, co         


        

Answer 1

I was trying to achieve the same without subquery and was able to get the required result as below

SELECT DISTINCT COUNT(*) OVER () AS TotalRecords
FROM temptable
GROUP BY column_1, column_2, column_3, column_4

Answer 2

A CTE worked for me:

with cte as (
  select 1 col1
  from temptable
  group by column_1
)

select COUNT(col1)
from cte;

Answer 3

You could do:

select sum(counts) total_records from (
    select count(*) as counts
    from temptable
    group by column_1, column_2, column_3, column_4
) as tmp

Answer 4

Following for PrestoDb, where FirstField can have multiple values:

select *
            , concat(cast(cast((ThirdTable.Total_Records_in_Group * 100 / ThirdTable.Total_Records_in_baseTable) as DECIMAL(5,2)) as varchar), '%') PERCENTage
from 
(
    SELECT FirstTable.FirstField, FirstTable.SecondField, SecondTable.Total_Records_in_baseTable, count(*) Total_Records_in_Group
    FROM BaseTable FirstTable
    JOIN (
            SELECT FK1, count(*) AS Total_Records_in_baseTable 
            FROM BaseTable
            GROUP BY FK1
        ) SecondTable
    ON FirstTable.FirstField = SecondTable.FK1
    GROUP BY FirstTable.FirstField, FirstTable.SecondField, SecondTable.Total_Records_in_baseTable
    ORDER BY FirstTable.FirstField, FirstTable.SecondField
) ThirdTable

Answer 5

The simplest solution is to use a derived table:

Select Count(*)
From    (
        Select ...
        From TempTable
        Group By column_1, column_2, column_3, column_4
        ) As Z

Another solution is to use a Count Distinct:

Select ...
    , ( Select Count( Distinct column_1, column_2, column_3, column_4 )
        From TempTable ) As CountOfItems
From TempTable
Group By column_1, column_2, column_3, column_4

Answer 6

How about using a COUNT OVER (PARTITION BY {column to group by}) partitioning function in SQL Server?

For example, if you want to group product sales by ItemID and you want a count of each distinct ItemID, simply use:

SELECT
{columns you want} ,
COUNT(ItemID) OVER (PARTITION BY ItemID) as BandedItemCount ,
{more columns you want}... ,
FROM {MyTable}

If you use this approach, you can leave the GROUP BY out of the picture -- assuming you want to return the entire list (as you might do report banding where you need to know the entire count of items you are going to band without having to display the entire set of data, i.e. Reporting Services).