使用行号更新列

Question

我有一个大表，需要在Teradata中为其添加行号。我在已经叫做row_num的表上有一列，但我需要用实际的数字来更新它。我试图使用下面的代码，但它不会工作。

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

如果你有一个标识列，它唯一标识每一行，你可以这样做：

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 
;