Add column with id in Oracle SQL

Question

Have a table in Oracle db such like this:

Word  Cnt
 A     20
 B     25
 C     23
 B     29
 D     31

What I trying to do - is to add an additional column with id of a word. But it is not a primary key it wont be unique because of repeating words. So the outcome I'm looking for is:

Word  Cnt   ID
 A     20   1
 B     25   2
 C     23   3
 B     29   2 
 D     31   4

How can I perform that in Oracle SQL?

Answer 1

You can use a window function to calculate the ID:

select word, 
       cnt, 
       dense_rank() over (order by word) as id
from the_table;

You can update the table using the above, if you really need to persist that:

merge into the_table tg
using (
  select rowid as rid,
         dense_rank() over (order by word) as new_id
  from the_table
) t on (t.rid = tg.rowid)
when matched then update
   set id = t.new_id;

Answer 2

My solution requires a lot of nested subqueries, but it works...

alter table mytable add (id number(12));

update mytable
  set id = (select n from 
              (select word, rownum n from 
                 (select word from mytable group by word order by word)
              ) x where mytable.word = x.word
           );

Answer 3

如果您的意图只是选择

  select word,cnt,count(*) over(partition by word,count) as Id from table_name;