Question

我有一个愚蠢的问题，我无法在Teradata中解决。

我有n个表，对于每个n个表（n> 1000），我必须得到表的列，这些列可能因表而异。

我的问题是：如何从字符串中的一个查询（例如Select columnName from dbc.columns where tablename = table1）获取结果，让我们说_vColumns，以便以后能够使用动态SQL语法中的排序值（_vColumns）？

Answer 1

我使用dbc.columns

完成了long ago

 /*** Rows to concatenated string ***/
 /*** Nested version instead of hundreds of CASEs.
       Returns a single concatenated string consisting of up to 2048
 columnnames ***/
SELECT
  databasename
 ,tablename
 ,max(case when rnk mod 16 = 0 then ColumnName else '' end) ||
  max(case when rnk mod 16 = 1 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 2 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 3 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 4 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 5 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 6 then ',' || ColumnName else '' end) ||
  max(case when rnk mod 16 = 7 then ',' || ColumnName else '' end)
 as Columns
from
 (
  sel
    databasename
   ,tablename
   ,rnk / 16 as rnk
   ,max(case when rnk mod 16 = 0 then ColumnName else '' end) ||
    max(case when rnk mod 16 = 1 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 2 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 3 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 4 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 5 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 6 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 7 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 8 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 9 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 10 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 11 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 12 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 13 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 14 then ',' || ColumnName else '' end) ||
    max(case when rnk mod 16 = 15 then ',' || ColumnName else '' end) as ColumnName
  from
   (
    select
      databasename
     ,tablename
     ,rnk / 16 as rnk
     ,max(case when rnk mod 16 = 0 then ColumnName else '' end) ||
      max(case when rnk mod 16 = 1 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 2 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 3 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 4 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 5 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 6 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 7 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 8 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 9 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 10 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 11 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 12 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 13 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 14 then ',' || ColumnName else '' end) ||
      max(case when rnk mod 16 = 15 then ',' || ColumnName else '' end) as ColumnName
    from
     (
      select
        databasename
       ,tablename
       ,trim(columnName) as ColumnName
       ,rank() over (partition by databasename, tablename
                     order by columnid) -1 as rnk
      from
        dbc.columns 
     ) dt
    group by 1,2,3 
   )dt
  group by 1,2,3
 )dt
group by 1,2

但是，从Td14.10开始，您应该使用dbc.Column V （如果您的任何列名超过30个字符），那么2048 * 128个字符将达到64000个字符的最大限制...

如何使用分隔符将列结果转换为单个字符串

1 个答案: