Question

我正在使用汽车制造作为一个例子，很适合我的情况。

我现在的示例查询，它给出了每个州的简单计数：

SELECT
  state as State,
  count(distinct(idnumber)) as Total
FROM
  database.table
WHERE
  make IN('honda', 'toyota', 'subaru')
GROUP BY
  state
ORDER BY
  state

请注意，这将为我提供每辆汽车的计数，不包括福特，雪佛兰等等。制造清单将是每个品牌。

有没有办法可以打破这一点，以便在不诉诸子查询的情况下向我提供每个州的计数？在我的脑海中，它就像在计数中有一个where语句（distinct（idnumber））select，但我不确定是否可能。

这就是我的想法：

SELECT
  state as State,
  count(distinct(idnumber)) as Total_State,
  (count(distinct(idnumber)) WHERE make = 'honda') as Total_Honda
WHERE
  make IN('honda', 'toyota', 'subaru')
GROUP BY
  state
ORDER BY
  state

Answer 1

您可以通过以下方式向群组添加多个列：

GROUP BY
  state, make

我可能会误解你的问题，但是你可以将两列分组，这样你就可以获得在CA中制作的ford数和在CA等中制作的hondas

要明确，您的查询将是：

SELECT
  state as State,
  count(distinct(idnumber)) as Total,
  make as Make
FROM
  database.table
WHERE
  make IN('honda', 'toyota', 'subaru')
GROUP BY
  state, make
ORDER BY
  state

就像一个有趣的测试一样，我这样做了：

create table `cars` (
`id` int(11),
`make` varchar(255),
`state` varchar(255)
);


insert into cars(id, make, state) values 
     (1, 'honda', 'ca'), (2, 'honda', 'ca'), (3, 'toyota', 'ca'), 
     (4, 'toyota', 'az'), (5, 'toyota', 'az'), (6, 'honda', 'az');


SELECT state as State, count(id) as Total, make as Make
FROM cars
WHERE make IN('honda', 'toyota', 'subaru')
GROUP BY state, make
ORDER BY state

回来了：

+-------+-------+--------+
| State | Total | Make   |
+-------+-------+--------+
| az    |     1 | honda  |
| az    |     2 | toyota |
| ca    |     2 | honda  |
| ca    |     1 | toyota |
+-------+-------+--------+

这是我的预期。那是你在想什么？

mysql可以选择count（distinct（id）where col ='value'）？

1 个答案: