SELECT COUNT(*) FROM bla WHERE Position = 'Manager'

在MySQL中，布尔表达式的计算结果为0或1，因此下面的聚合工作:

select sum(Position = 'Manager') as ManagerCount
from ...

如果使用SQL 2005或更高版本，也可以使用Pivot关键字

更多信息来自Technet

SELECT *
FROM @Users
PIVOT (
    COUNT(Position)
    FOR Position
    IN (Manager, CEO, Employee)
) as p

测试数据集

DECLARE @Users TABLE (Position VARCHAR(10))
INSERT INTO @Users (Position) VALUES('Manager')
INSERT INTO @Users (Position) VALUES('Manager')
INSERT INTO @Users (Position) VALUES('Manager')
INSERT INTO @Users (Position) VALUES('CEO')
INSERT INTO @Users (Position) VALUES('Employee')
INSERT INTO @Users (Position) VALUES('Employee')
INSERT INTO @Users (Position) VALUES('Employee')
INSERT INTO @Users (Position) VALUES('Employee')
INSERT INTO @Users (Position) VALUES('Employee')
INSERT INTO @Users (Position) VALUES('Employee')

注意使用PrestoDB SQL(来自Facebook)，有一个快捷方式:

https://prestodb.io/docs/current/functions/aggregate.html

Count_if (x)→bigint 返回TRUE输入值的个数。这 函数等价于count(CASE WHEN x THEN 1 END)

以下是我所做的，以获得一个数据集，其中包括每个集装箱内满足标准的总数和数量。让我来回答这个问题"有多少集装箱的货物超过X%大于51号"

select
   Schedule,
   PackageNum,
   COUNT (UniqueID) as Total,
   SUM (
   case
      when
         Size > 51 
      then
         1 
      else
         0 
   end
) as NumOverSize 
from
   Inventory 
where
   customer like '%PEPSI%' 
group by
   Schedule, PackageNum

如果使用Postgres或SQLite，可以使用Filter子句来提高可读性:

SELECT
  COUNT(1) FILTER (WHERE POSITION = 'Manager') AS ManagerCount,
  COUNT(1) FILTER (WHERE POSITION = 'Other') AS OtherCount
FROM ...

BigQuery也有Countif -在这里可以看到不同SQL方言对这些特性的支持: https://modern-sql.com/feature/filter