简化CTE字符串连接？

Question

我有以下代码清单

Code Meaning 
1    Single 
2    Married/Separate 
3    Divorced 
4    Widowed 
8    Not Applicable 
99   Not known

我试图使用CTE将这些展平为一行.我有一个CTE解决方案,它使用RowNumber函数来执行此操作.

WITH Flattened (JoinItem, CodeMeaning) AS
(
    SELECT 1 AS JoinItem, CAST('' AS VARCHAR(255))
    UNION ALL
    SELECT f.JoinItem+1, CAST(f.CodeMeaning + ',' + c.CodeMeaning AS VARCHAR(255))
    FROM
    (
        SELECT JoinItem = ROW_NUMBER() OVER (ORDER BY Code),c.Code + ' - ' + c.Meaning AS CodeMeaning
        FROM Codes c
    ) c
    INNER JOIN Flattened f
    ON f.JoinItem=c.JoinItem
)
SELECT TOP 1 JoinItem,  CodeMeaning 
FROM Flattened 
ORDER BY JoinItem DESC

但是,我想知道我是否可以在不使用RowNumber函数但仍使用CTE的情况下执行此操作.所以我有以下内容 - 我认为更简单 - Sql

WITH Flattened (JoinItem, CodeMeaning) AS
(
    SELECT 1 AS JoinItem, CAST('' AS VARCHAR(255))
    UNION ALL
    SELECT c.JoinItem, CAST(f.CodeMeaning + ',' + c.CodeMeaning AS VARCHAR(255))
    FROM
    (
        SELECT 1 AS JoinItem,c.Code + ' - ' + c.Meaning AS CodeMeaning
        FROM Codes c            
    ) c
    INNER JOIN Flattened f
    ON f.JoinItem=c.JoinItem
)
SELECT JoinItem, odeMeaning 
FROM Flattened 

现在它正在最大化递归并产生类似于笛卡尔联合的东西 - 如果不是更糟!

我想尝试让它每次使用固定的"JoinItem"加入锚记录

因此,如果有解决方案,任何指向我出错的地方都会有所帮助.

编辑SqlFiddle

Answer 1

假设这是SQL Server,你考虑过这样的事情:

select stuff((select ',' + c.code + '-' + c.Meaning
              from codes c
              order by code
              for xml path ('')
             ), 1, 1, '')

编辑:

要使用CTE执行此操作,请先定义序列号,然后执行展平:

with c as (
      select row_number() over (order by code) as seqnum, c.code + '-' + c.meaning as CodeMeaning
      from codes c
     ),
     flattened as (
      select CodeMeaning as CodeMeaning
      from c
      where rownum = 1
      union all
      select f.CodeMeaning + ',' + c.CodeMeaning
      from c join
           flattened f
           on c.seqnum = f.seqnum + 1
     )
select *
from flattened;

如果列表太长,则可能必须增加默认递归级别.