Teradata:将重复值转换为逗号分隔字符串的结果 [英] Teradata: Results with duplicate values converted into comma delimited strings

问题描述

我有一个典型的表格，其中每一行代表一个客户 - 产品持有量.如果一个客户有多个产品，那么会有多行具有相同的客户 ID.我正在尝试将其汇总起来，以便每个客户都由一行表示，所有产品代码都连接在一个逗号分隔的字符串中.下图说明了这一点

I have a typical table where each row represents a customer - product holding. If a customer has multiple products, there will be multiple rows with the same customer Id. I'm trying to roll this up so that each customer is represented by a single row, with all product codes concatenated together in a single comma delimited string. The diagram below illustrates this

在谷歌搜索之后，我设法使用 XMLAGG 函数让它工作 - 但这仅适用于一小部分数据，当扩展时 Teradata 抱怨假脱机空间"用完 - 所以我认为它不是很高效.

After googling this, I managed to get it to work using the XMLAGG function - but this only worked on a small sample of data, when scaled up Teradata complained about running out of 'spool space' - so I figure it's not very efficient.

有人知道如何有效地实现这一目标吗?

Does anyone know how to efficiently achieve this?

推荐答案

较新版本的 Teradata 支持 NPath，可用于此目的.你必须习惯语法，它是一个表运算符 :-)

Newer versions of Teradata support NPath, which can be used for this. You have to get used to the syntax, it's a Table Operator :-)

例如这将返回系统中每个表的列列表:

E.g. this returns the column list for each table in your system:

SELECT * 
FROM 
   NPath(ON(SELECT databasename, tablename, columnname, columnid 
            FROM dbc.columnsV
           ) AS dt                            -- input data
         PARTITION BY databasename, tablename -- group by columns
         ORDER BY columnid                    -- order within list
         USING
           MODE (NonOverlapping)              -- required syntax 
           Symbols (True AS F)                -- every row
           Pattern ('F*')                     -- is returned
           RESULT(First (databasename OF F) AS DatabaseName, -- group by column
                  First (tablename OF F) AS TableName,       -- group by column
                  Count (* OF F) AS Cnt,
                  Accumulate(Translate(columnname USING unicode_to_latin) OF ANY (F)) AS ListAgg
                 )
        );

应该比 XMLAgg 好.

Should be waaaaaay better than XMLAgg.

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