在MSSQL中使用CASE语句的最小MAX

Question

我有这样一张桌子。我要输入的所有国家名称，人口编号，以及如果MAX中的人口，则标记MAX，并类似地标记MIN。我已经在下面使用CASE语句在MSSQL中编写了查询。

/* MIN/MAX Population amongst the countries */
SELECT country, population,
    CASE
        WHEN population == MIN(population) THEN "MIN"
        WHEN population == MAX(population) THEN "MAX" ELSE "NA"
    END as "pop_stats"
FROM countries_by_population;

Answer 1

使用over()使其成为没有分区的窗口函数：

SELECT country, population,
    CASE
        WHEN population == MIN(population) over() THEN "MIN"
        WHEN population == MAX(population) over() THEN "MAX" ELSE "NA"
    END as "pop_stats"
FROM countries_by_population;

Answer 2

Demo on db<>fiddle

首先，应该通过如下所示存储@Min_Population和@Max_Population

DECLARE @Min_Population decimal(18,2), @Max_Population decimal(18,2)
SELECT @Min_Population = MIN(population), @Max_Population = MAX(population)
FROM countries_by_population

[之后，您可以像这样比较每个项目的值（请注意，SQL中的字符用单引号而不是双引号封闭）

CASE
    WHEN population = @Min_Population THEN 'MIN'
    WHEN population = @Max_Population THEN 'MAX' ELSE 'NA'
END as pop_stats

完整查询

DECLARE @Min_Population decimal(18,2), @Max_Population decimal(18,2)
SELECT @Min_Population = MIN(population), @Max_Population = MAX(population)
FROM countries_by_population

SELECT country, population,
    CASE
        WHEN population = @Min_Population THEN 'MIN'
        WHEN population = @Max_Population THEN 'MAX' ELSE 'NA'
    END as pop_stats
FROM countries_by_population;