SQL 服务器 Row_number 按个案排序

Question

编辑了整个主题。

我需要创建一个按类型对文章进行排序的视图。

如果我只有类型：*VALUE -> 我只需要显示这一行。
如果我有以下类型：*VALUE & 2 -> 仍然显示与 *VALUE 类型相应的行。
如果我只有类型 : 2 -> 显示这个。

我已经做了这样的事情:

VALUE* 是一个值，应该来自另一个 table 和一个 Join。

SELECT Id_item ,Name_item , Type_item , Id_type_item 来自项目 WHERE Name_item = 'Gillette' AND (Id_Type_item = VALUE* OR Id_Type_item ='10')<br> 按情况订购 WHEN row_number() OVER(ORDER BY Id_item DESC , Id_Type_Item DESC) <= 1 THEN 0 其他 1 结束;

但如果我们有两行类型 (*VALUE & 10):

Id_item / Name_item / Type_item / Id_Type_Item
1       Gillette    45            30 (*VALUE)
1       Gillette    2             10

所以我认为 Over() 上的顺序对于始终按 *VALUE 排序很有用（实际上是另一个 table 的另一列）

我一直想要select只有1行数据！ :)

Answer 1

我猜，您想要的是每个 SELECT 返回的 "first" 行？无需为同一 table 上的每个变量使用单独的 SELECT 语句，您可以使用 window 函数来执行此操作。我相信这就是您想要的。

WITH CTE AS(
    --The following assumes table A and B have the same DDL (which begs the question, why are they different tables?)
    SELECT *,
           ROW_NUMBER() OVER (PARTITION BY var
                              ORDER BY (SELECT NULL)) AS RN --Replace SELECT(NULL) with your actual ordering criteria
    FROM A
    WHERE var IN (1,2)
    UNION --ALL(?)
    SELECT *
           ROW_NUMBER() OVER (PARTITION BY var
                              ORDER BY (SELECT NULL)) AS RN --Replace SELECT(NULL) with your actual ordering criteria
    FROM B
    WHERE var IN (3))
SELECT *
FROM CTE
WHERE RN = 1;

Answer 2

这是一个可能的解决方案。在这种情况下 ROW_NUMBER、RANK 和 DENSE_RANK 都可以。但是，ROW_COUNT 在 sql 服务器中不是有效的 window 函数。

DECLARE @A TABLE(ID INT, Value INT)
DECLARE @B TABLE(ID INT,Value INT)
INSERT INTO @A VALUES (1,1),(2,1),(3,2),(4,3),(5,2),(6,1),(7,3)
INSERT INTO @B VALUES (1,1),(2,1),(3,1),(4,2),(5,3),(6,2),(7,1),(8,3)

;WITH D AS
(
    SELECT ID,Value FROM @A WHERE Value IN(1,2)
    UNION ALL
    SELECT ID,Value FROM @B WHERE Value IN (3)
 )
SELECT * FROM
(
    SELECT
      ID, Value,
      ValueRankInSet = DENSE_RANK() OVER(PARTITION BY VALUE ORDER BY ID) -- <-- If you do not have an ID field you can subst ID with NEWID() as order is not important 
    FROM D
)AS X
WHERE ValueRankInSet = 1

Answer 3

在您的 Select(s) 中分配优先级，然后在 row_number 中按优先级排序：

with cte as 
 (
    SELECT *,
       row_number()
       over (-- partition by ??? 
             order by prio) as Position
    FROM 
    (
    SELECT 1 as prio, * FROM A WHERE var = 1
    UNION -- probably a more efficient UNION ALL
    SELECT 2 as prio, * FROM A WHERE var = 2
    UNION -- probably a more efficient UNION ALL
    SELECT 3 as prio, * FROM B WHERE var = 3
    )
 )
select *
from cte
WHERE Position = 1

SQL 服务器 Row_number 按个案排序

SQL Server Row_number in ORDER BY CASE

sql

sql-server

case

row-number

sql-order-by