Question

我有一个大表，需要在Teradata中添加行号。我在表上有一个名为row_num的列，但我需要用实际数字更新它。我试过使用下面的代码，但它不会起作用。

update database.time
set row_num = INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY
(START WITH 1
INCREMENT BY 1
MINVALUE 1
NO CYCLE))

任何帮助将不胜感激。谢谢！

Answer 1

如果您有一个唯一标识每一行的标识列，您可以执行以下操作：

update t
    set t.row_num = tt.seqnum
    from database.time t,
         (select t.*, row_number() over (order by id) as seqnum
          from database.time t
         ) tt
    where t.id = tt.id;

Answer 2

update  t

from    mytable t 
      ,(select     t.*
                   ,cast( row_number() over (order by id) as bigint) as rn

        from        mytable t
        ) tt

set     row_num = tt.rn

where   t.id = tt.id
;

使用行号更新列

2 个答案: