Question

我有一个带有属性

的表count

COUNT1
COUNT2
共3个记录
count4
count5

我想选择一个具有最大价值的列。我该怎么做？

计数表示页面命中，我想选择一个具有最大命中数的列并显示它。

Answer 1

您可以使用双嵌套子查询

select 
  (select max(count1)
   from (
    select count1 union all
    select count2 union all
    select count3 union all
    select count4 union all
    select count5) X) as MaxCount
from tbl

Answer 2

有几种方法，涉及PIVOT或Temp Table，但我认为最容易理解的是使用Case。

SELECT
    CASE
        WHEN count1 >= count2 AND count2 >= count3 AND count1 >= count4 AND count1 >= count5 THEN count1
        WHEN count2 >= count3 AND count2 >= count4 AND count2 >= count5 THEN count2
        WHEN count3 >= count4 AND count3 >= count5 THEN count3
        WHEN count4 >= count5 THEN count4
        ELSE count5
    END AS highestCount

Answer 3

   select MAX(max_count) FROM
   (
   select  count1 as max_count from count 
   UNION
   select  count2 as max_count from count 
   UNION
   select  count3 as max_count from count 
   UNION
   select  count4 as max_count from count 
   UNION 
   select  count4 as max_count from count
   )

我不建议使用Select，因为生成相同需要花费大量时间。触发器会更好

根据最大值选择列

3 个答案: