SQL:在单个字段中包含多个值的嵌套 SELECT

Question

在我的 SQL 2005 数据库中，我有一个表，其中的值存储为 ID，并与其他表有关系。因此，在我的 MyDBO.warranty 表中，我存储了 Product_id 而不是 Product_name 以节省空间。产品名称存储在 MyDBO.products 中。

当营销部门提取人口统计信息时，查询会从相关表中为每个 ID 选择相应的名称(为简洁起见，进行了精简):

SELECT w1.warranty_id AS "No.",
       w1.created AS "Register Date" 
       w1.full_name AS "Name", 
       w1.purchase_date AS "Purchased", 
       (
           SELECT p1.product_name
           FROM WarrDBO.products p1 WITH(NOLOCK)
           WHERE p1.product_id = i1.product_id
       ) AS "Product Purchased",
       i1.accessories
FROM WarrDBO.warranty w1
LEFT OUTER JOIN WarrDBO.warranty_info i1
    ON i1.warranty_id = w1.warranty_id
ORDER BY w1.warranty_id ASC

现在，我的问题是 Warranty_info 表中的“accessories”列存储了多个值:

No.     Register Date    Name             Purchased       Accessories
---------------------------------------------------------------------
1500    1/1/2008         Smith, John      Some Product    5,7,9
1501    1/1/2008         Hancock, John    Another         2,3
1502    1/1/2008         Brown, James     And Another     2,9

我需要对“Accessories”执行与“Product”类似的操作，并从 MyDBO.accessories 表中提取 accessory_name使用accessory_id。我不知道从哪里开始，因为首先我需要提取 ID，然后以某种方式将多个值连接成一个字符串。所以每一行都会有“accessoryname1，accessoryname2，accessoryname3”:

No.     Register Date    Name             Purchased       Accessories
---------------------------------------------------------------------
1500    1/1/2008         Smith, John      Some Product    Case,Bag,Padding
1501    1/1/2008         Hancock, John    Another         Wrap,Label
1502    1/1/2008         Brown, James     And Another     Wrap,Padding

我该怎么做？

编辑>>发布我的最终代码:

我创建了这个函数:

CREATE FUNCTION SQL_GTOInc.Split
(
  @delimited varchar(50),
  @delimiter varchar(1)
) RETURNS @t TABLE
(
-- Id column can be commented out, not required for sql splitting string
  id INT identity(1,1), -- I use this column for numbering splitted parts
  val INT
)
AS
BEGIN
  declare @xml xml
  set @xml = N'<root><r>' + replace(@delimited,@delimiter,'</r><r>') + '</r></root>'

  insert into @t(val)
  select
    r.value('.','varchar(5)') as item
  from @xml.nodes('//root/r') as records(r)

  RETURN
END

并相应地更新了我的代码:

SELECT w1.warranty_id, 
       i1.accessories,
       (
           CASE
               WHEN i1.accessories <> '' AND i1.accessories <> 'NULL' AND LEN(i1.accessories) > 0 THEN
                   STUFF(
                       (
                           SELECT ', ' + a1.accessory
                           FROM MyDBO.accessories a1
                           INNER JOIN MyDBO.Split(i1.accessories, ',') a2
                           ON a1.accessory_id = a2.val
                           FOR XML PATH('')
                       ), 1, 1, ''
                   )
               ELSE ''
           END
        ) AS "Accessories"
FROM MyDBO.warranty w1
    LEFT OUTER JOIN MyDBO.warranty_info i1
    ON i1.warranty_id = w1.warranty_id

Answer 1

您可以编写一个表值函数，该函数只需将逗号分隔的字符串拆分为 XML 并将 XML 节点转换为行。

参见: http://www.kodyaz.com/articles//t-sql-convert-split-delimeted-string-as-rows-using-xml.aspx

通过函数调用的结果连接到附件，并将结果填充回逗号分隔的名称列表。

未经测试的代码:

SELECT w1.warranty_id AS "No.",
       w1.created AS "Register Date" 
       w1.full_name AS "Name", 
       w1.purchase_date AS "Purchased", 
       (
           SELECT p1.product_name
           FROM WarrDBO.products p1 WITH(NOLOCK)
           WHERE p1.product_id = i1.product_id
       ) AS "Product Purchased",
       STUFF(
         (
           SELECT 
             ', ' + a.name
           FROM [table-valued-function](i1.accessories) acc_list 
             INNER JOIN accessories a ON acc_list.id = a.id
           FOR XML PATH('')
         ), 1, 1, ''
       ) AS [accessories]
FROM WarrDBO.warranty w1
  LEFT OUTER JOIN WarrDBO.warranty_info i1
    ON i1.warranty_id = w1.warranty_id
ORDER BY w1.warranty_id ASC