如何计算查询分组返回的记录数，

例如：

select count(*) 
from temptable
group by column_1, column_2, column_3, column_4

给我，

1
1
2

我需要计算以上记录才能得到1 + 1 + 1 = 3。

您可以在另一个COUNT上使用OVER子句在两个查询中同时进行

select
    count(*) RecordsPerGroup,
    COUNT(*) OVER () AS TotalRecords
from temptable
group by column_1, column_2, column_3, column_4

最简单的解决方案是使用派生表：

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

另一个解决方案是使用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

我知道已经很晚了，但是没有人建议这样做：

select count ( distinct column_1, column_2, column_3, column_4) 
from   temptable

至少这在Oracle中有效-我目前没有其他数据库可以对其进行测试，并且我对T-Sql和MySQL语法不太熟悉。

此外，我也不完全确定解析器是否可以通过这种方式更有效，或者其他人嵌套select语句的解决方案是否更好。但是从编码的角度来看，我认为它更优雅。

我试图在没有子查询的情况下达到同样的效果，并且能够获得所需的结果，如下所示

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

CTE为我工作：

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

select COUNT(col1)
from cte;

怎么样：

SELECT count(column_1)
FROM
    (SELECT * FROM temptable
    GROUP BY column_1, column_2, column_3, column_4) AS Records

您可以这样做：

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

在PostgreSQL中，这对我有用：

select count(count.counts) 
from 
    (select count(*) as counts 
     from table 
     group by concept) as count;

您可以执行以下代码吗？它在Oracle中工作。

SELECT COUNT(COUNT(*))
FROM temptable
GROUP BY column_1, column_2, column_3, column_4

您还可以通过以下查询获得

select column_group_by,count(*) as Coulm_name_to_be_displayed from Table group by Column;

-- For example:
select city,count(*) AS Count from people group by city

试试这个查询：

select top 1 TotalRows = count(*) over () 
from yourTable
group by column1, column2

以下是PrestoDb，其中FirstField可以具有多个值：

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

在SQL Server中使用COUNT OVER（PARTITION BY {列为分组依据））分区功能如何？

例如，如果要按ItemID对产品销售进行分组，并且希望对每个不同的ItemID进行计数，则只需使用：

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

如果您使用这种方法，则可以将GROUP BY排除在外-假设您想返回整个列表（因为您可能需要进行报告分组，因此您需要知道要分组的项目总数，而不必以显示整个数据集，即Reporting Services）。