Oracle:使用ROWNUM和ORDER BY子句更新表列

Question

我想填充一个带有运行整数的表列,所以我想使用ROWNUM.但是,我需要根据其他列的顺序填充它,例如ORDER BY column1, column2.遗憾的是,由于Oracle不接受以下声明,因此不可能:

UPDATE table_a SET sequence_column = rownum ORDER BY column1, column2;

也不是以下语句(尝试使用WITH子句):

WITH tmp AS (SELECT * FROM table_a ORDER BY column1, column2)
UPDATE tmp SET sequence_column = rownum;

那么如何使用SQL语句并且不依赖于PL/SQL中的游标迭代方法呢？

Answer 1

这应该工作(适合我)

update table_a outer 
set sequence_column = (
    select rnum from (

           -- evaluate row_number() for all rows ordered by your columns
           -- BEFORE updating those values into table_a
           select id, row_number() over (order by column1, column2) rnum  
           from table_a) inner 

    -- join on the primary key to be sure you'll only get one value
    -- for rnum
    where inner.id = outer.id);

或者您使用该MERGE声明.像这样的东西.

merge into table_a u
using (
  select id, row_number() over (order by column1, column2) rnum 
  from table_a
) s
on (u.id = s.id)
when matched then update set u.sequence_column = s.rnum