Question

我有一个像下面的查询得到错误 - 'SELECT DISTINCT，ORDER BY表达式必须出现在选择列表中'

 select distinct name
    from fruits
  order by case
   when name = 'mango' then 1
    else 2
   end

这会产生4条记录，比如说

apple, mango, pear and grape

我怎样才能确保我将Mango作为第一张唱片，其余的则随之而来。我尝试使用case语句，但无法获得所需的结果。任何想法将不胜感激。

Answer 1

我相信这应该完成你所描述的需要。

select distinct 
       name,
       case name when 'Mango' then 1 else 2 end as fruitOrder
from   fruits
order by 
       fruitOrder

Answer 2

如果您需要始终将'mango'放在第一个位置，无论其他行如何，这可能是一种方式：

with fruits(name) as (
    select 'apple' from dual union all
    select 'mango' from dual union all
    select 'pear'  from dual union all
    select 'grape' from dual
)
select name
from fruits
order by case
            when name = 'mango' then 1
            else 2
         end

如果您需要添加DISTINCT，这应该有效：

select distinct name,
        case
            when name = 'mango' then 1
            else 2
         end orderCol
from fruits
order by orderCol

Answer 3

这将为您提供“芒果”，其他按顺序排列;

WITH get_rows AS
(SELECT DISTINCT item_type
   FROM the_item)
SELECT item_type
  FROM 
(SELECT 1 as seq, item_type
   FROM get_rows
  WHERE item_type = 'Mango'
 UNION ALL
 SELECT 2 as seq, item_type
   FROM get_rows
  WHERE item_type <> 'Mango')
ORDER BY seq, item_type

在选择中使用带有DISTINCT的CASE的违规行为

3 个答案: