分配組號條件

Question

我們有如下所示

一個表，我們要寫入與生成組ID查詢（基於以下）

如果一個國家然後[國家，類別]組記錄應該被分配一個唯一的組ID，

所以對於上面的表，我們需要編寫單個查詢（沒有存儲過程或功能）這將返回如下結果。

我們試圖查詢其模樣非常複雜，無法讀取。

所以我們正在尋找更好的查詢來實現相同。

預先感謝您

Answer 1

假設SQL Server中，您可以通過DENSE_RANK()加入OVER()到COUNT()和使用CASE語句做到這一點：

;with cte AS (SELECT *,COUNT(*) OVER(PARTITION BY Country,Category) CT 
         ,CASE WHEN Category IS NOT NULL THEN DENSE_RANK() OVER (ORDER BY Country) END Rank_ 
       FROM Table1) 
SELECT Country 
     ,State 
     ,Category 
     ,CASE WHEN CT > 1 AND Rank_ IS NOT NULL THEN DENSE_Rank() OVER(ORDER BY Rank_ DESC) END AS Group_ 
FROM cte 
ORDER BY Country DESC,State 

演示：SQL Fiddle

只有當你關心它從1-n開始編號是否需要多個DENSE_RANK()。

Answer 2

您可以在SQL Server這樣做，因爲：

select t.*, cs.groupnum 
from table t left outer join 
    (select country, category, count(*) as cnt, 
      dense_rank() over (order by country, category) as groupnum 
     from table t 
     group by country, category 
     having count(*) > 1 
    ) cs 
    on t.country = cs.country and t.category = cs.category; 

在MySQL中，你可以做這個使用變量而不是dense_rank()的變體。

Answer 3

如果你使用MySQL，你可以使用以下命令：

小提琴：http://sqlfiddle.com/#!2/0f381/7/0

select t.country, t.state, t.category, v.grp 
    from (select x.*, @r := @r + 1 as grp 
      from (select country, category 
        from tbl 
       where category is not null 
       group by country, category 
       having count(*) > 1 
       order by category, state, country) x 
     cross join (select @r := 0) r) v 
right join tbl t 
    on v.country = t.country 
    and v.category = t.category 

Answer 4

DROP TABLE #TEST 

GO 

CREATE TABLE #Test(
    Country NVARCHAR(100) 
    ,[State] NVARCHAR(100) 
    ,Category NVARCHAR(100) 
    ,GroupID INT); 

GO 

INSERT INTO #Test 
    (Country, State, Category) 
VALUES 
    ('US','AZ','G1'), 
    ('US','AL','G1'), 
    ('US','NY',null), 
    ('UK','TN','G1'), 
    ('UK','MH','G1'), 
    ('UK','AP','G3'), 
    ('CA','MI',null), 
    ('CA','CA',null); 


UPDATE 
    T2 
SET 
    T2.GroupID = T.RANKED_ID 
FROM 
    (SELECT COUNT(*) 'Count' 
      ,Country 
      ,Category 
      ,DENSE_RANK() OVER (ORDER BY Country DESC) AS Ranked_ID 
     FROM #Test 
     WHERE Category IS NOT NULL 
     GROUP BY Country, Category 
     HAVING COUNT(*) > 1 
    ) AS T 
    JOIN #Test T2 
    ON T.Category = T2.Category 
    AND T.Country = T2.Country 


SELECT * 
FROM #TEST