Question

我在表格中有以下数据： -

| item    | rate |
-------------------
| a       | 50   |
| a       | 12   |
| a       | 26   |
| b       | 12   |
| b       | 15   |
| b       | 45   |
| b       | 10   |
| c       | 5    |
| c       | 15   |

我需要一个返回以下输出的查询：

| item no | rate |
------------------
| a       | 12 |  --from (26 , 12 , 50)
| b       | 45 | --from (12 ,15 , 45 , 10)
| c       | 5  | --from (5 , 15)

，即item_no应该是不同的，并且随机有一个速率值..

提前致谢

Answer 1

一种方法是使用行号窗口函数item作为分区。然后在每个分区中使用ORDER BY NEWID()生成随机排序，任意保留每个item分区的第一行。

SELECT t.item,
       t.rate
FROM
(
    SELECT item,
           rate,
           ROW_NUMBER() OVER(PARTITION BY item ORDER BY NEWID()) AS rn
    FROM yourTable
) t
WHERE t.rn = 1

Answer 2

HERE NEWID()用于分区以生成随机排序，
在分区内，它将保留每个项目的第一行。

with cte as
    (

        SELECT item,
               rate,
               ROW_NUMBER() OVER(PARTITION BY item ORDER BY NEWID()) AS rn
        FROM #Table1
        )
        select item,rate from cte where rn=1

Answer 3

WITH
CTE
AS
(
    SELECT DISTINCT
        item
    FROM T
)
SELECT
    CTE.item
    ,A.rate
FROM
    CTE
    CROSS APPLY
    (
        SELECT TOP(1) 
            T.rate
        FROM T
        WHERE T.item = CTE.item
        ORDER BY CRYPT_GEN_RANDOM(4)
    ) AS A
;

(item) include (rate)上的索引会有所帮助。

Answer 4

尝试此查询一次。

select * into #temp  from (
        SELECT 'a' item,50 rate 
        UNION ALL
        SELECT 'a',12  
        UNION ALL
        SELECT 'a', 26 
        UNION ALL
        SELECT 'b',12  
        UNION ALL
        SELECT 'b', 15 
        UNION ALL
        SELECT 'b',10 
        UNION ALL
        SELECT 'c',5  
        UNION ALL
        SELECT 'c',15 )as a

    select * from (
    select *,row_number()over(partition by item  ORDER BY newid() )as runm from #temp
    ) as a
    where runm=1

注意：上述查询每次都将新输出作为newid（）为每次执行生成一个新的id。

Answer 5

; WITH tb( item, rate)AS(
    SELECT 'a',50 UNION
    SELECT 'a',12  UNION
    SELECT 'a', 26 UNION
    SELECT 'b',12  UNION
    SELECT 'b', 15 UNION
    SELECT 'b',10 UNION
    SELECT 'c',5  UNION
    SELECT 'c',15 
    ) 
    SELECT * FROM (
        SELECT *,ROW_NUMBER()OVER( PARTITION BY item ORDER BY NEWID())  AS rn FROM tb
    ) t WHERE t.rn=1

根据不同的值从列中选择随机值

5 个答案: