Question

我的数据表包含如下数据：

Data         category
------------------------
apple        fruits
spinach      vegetables
mango        fruits
lion         animals
grapes       fruits
tiger        animals
potato       vegetables

我希望查询显示如下数据：

vegetables
spinach
potato 
fruits   
mango               
grapes
animals
lion       
tiger

Answer 1

首先，您必须正确设计架构，我认为它可能会对您有所帮助

IF OBJECT_ID('dbo.category') IS NOT NULL
    DROP TABLE category

CREATE TABLE category (
    categoryID INT Identity PRIMARY KEY
    ,categoryName VARCHAR(200)
    )

INSERT  INTO category(categoryName)
SELECT 'fruits'    Union all 
SELECT 'vegetables'Union all
SELECT 'animals'

SELECT * from category


IF OBJECT_ID('dbo.Datacategory') IS NOT NULL
Drop Table Datacategory

CREATE TABLE Datacategory (
    DatacategoryID INT Identity
    ,categoryID INT CONSTRAINT FK_Datacategory_category FOREIGN KEY REFERENCES category(categoryID)
    ,Data VARCHAR(200)
    )

INSERT INTO Datacategory(Data,categoryID)
SELECT     'apple'    ,1  Union all
SELECT     'spinach'  ,2  Union all
SELECT     'mango'    ,1  Union all
SELECT     'lion'     ,3  Union all
SELECT     'grapes'   ,1  Union all
SELECT     'tiger'    ,3  Union all
SELECT     'potato'   ,2

查询以获得所需结果

SELECT ISNULL(CAST(NULLIF(CASE 
                    WHEN RNo = 1
                        THEN categoryID
                    ELSE ''
                    END, '') AS VARCHAR), '') AS categoryID
    ,Data
FROM (
    SELECT D.categoryID
        ,D.Data
        ,ROW_NUMBER() OVER (
            PARTITION BY D.categoryID ORDER BY D.categoryID
            ) AS Rno
    FROM Datacategory d
    INNER JOIN category c ON c.categoryID = d.categoryID
    ) Dt
ORDER BY Dt.categoryID

输出

categoryID  Data
----------------
1           apple
            mango
            grapes
2           potato
            spinach
3           lion
            tiger

按列分组为SQL Server中的一行

1 个答案: