Question

我有一个名为“压力”的列，它的文本值（高，低，正常）在表中针对不同的个人重复了几次。现在，我想分别对高，低和正常值进行计数，并在三列中分别显示，如下所示。

pressure    high    low   Normal
            ??      ??     ??

请建议...

致谢

Answer 1

假设您有这样的查询：

SELECT
    SampleDateTime,    -- datetimeoffset(7) NOT NULL
    Celsius            -- float             NOT NULL
FROM
    Temperatures
ORDER BY
    SampleDateTime

然后您可以执行以下操作：

SELECT
    MAX( Celsius ) AS [High],
    MIN( Celsius ) AS [Low],
    AVG( Celsius ) AS [Mean],
    PERCENTILE_CONT( 0.5 ) WITHIN GROUP ( ORDER BY Celsius ) OVER () AS [Median]
FROM
    Temperatures

如果要使用模态值，则要涉及更多。由于这可能是连续数据，因此您需要ROUND以获得离散值

SELECT
    TOP 1
    ROUND( Celsius, 0 ) AS [Mode]
FROM
    Temperatures
GROUP BY
    Celsius
ORDER BY
    COUNT(*) DESC

...可以使用CROSS JOIN进行连接，因为每个子查询仅返回单行，所以可以：

SELECT
    [High],
    [Low],
    [Mean],
    [Median],
    [Mode]
FROM
    (
        SELECT
            MAX( Celsius ) AS [High],
            MIN( Celsius ) AS [Low],
            AVG( Celsius ) AS [Mean],
            PERCENTILE_CONT( 0.5 ) WITHIN GROUP ( ORDER BY Celsius ) OVER () AS [Median]
        FROM
        Temperatures
    ) AS t1
    CROSS JOIN
    (
        SELECT
            TOP 1
            ROUND( Celsius, 0 ) AS [Mode]
        FROM
            Temperatures
        GROUP BY
            Celsius
        ORDER BY
            COUNT(*) DESC
    ) AS t2

Answer 2

具有这样的表模式（包括示例数据）：

create table pressure(name varchar(10), pressure varchar(10));

insert into pressure(name, pressure) values("john", "high");
insert into pressure(name, pressure) values("john", "low");
insert into pressure(name, pressure) values("john", "normal");
insert into pressure(name, pressure) values("jacob", "high");
insert into pressure(name, pressure) values("smith", "normal");

一种方法是查询如下内容：

select 'pressure' as data, (select count(*) from pressure where pressure = 'high') as high, (select count(*) low from pressure where pressure = 'low') as low, (select count(*) normal from pressure where pressure = 'normal') as normal from dual;

这应该导致如下结果：

|   data   | high | low | normal |
| pressure |   2  |  1  |    2   |

免责声明：这可能不适用于大量数据

Answer 3

我认为您需要遵循这些原则

select 'pressure' as data, 
sum(case when pressure='high' then 1 else 0 end) as high,
sum(case when pressure='low' then 1 else 0 end) as low,
sum(case when pressure='normal' then 1 else 0 end) as normal
from your_table

如何在SQL中将列值显示为三列

3 个答案: