Question

I have a table which looks like this.

NAME    AGE
james   22
ames    12
messi   32
....
....

I can query this table using Select name, age from emp;

Now what I want is having an extra column before name which will be 1,2,3..N if the query return n rows.

SEQUENCE    NAME    AGE
1    james  22
2    ames   12
3    messi  32
4    ....
    ....

How I can do this?

Answer 1

if you want to just add a column which will contain sequence number at display time(not actually store that data in a table) you can use ROWNUM pseudocolumn or row_number() analytical function.

select row_number() over(order by name) seq
     , name
     , age
  from your_table

      SEQ NAME               AGE
---------- ----------- ----------
         1 ames                12
         2 james               22
         3 messi               32

The output of the above query is ordered by NAME but you can order by any column or combination of columns you want.

Second approach is using rownum pseudocolumn. result is ordered by name also

 select rownum seq
      , name
      , age
   from ( select name
               , age
           from your_table
          order by name
         )



       SEQ NAME               AGE
---------- ----------- ----------
         1 ames                12
         2 james               22
         3 messi               32