Rownum in postgresql

Question

Is there any way to simulate rownum in postgresql ?

Answer 1

If you have a unique key, you may use COUNT(*) OVER ( ORDER BY unique_key ) as ROWNUM

SELECT t.*, count(*) OVER (ORDER BY k ) ROWNUM 
FROM yourtable t;

| k |     n | rownum |
|---|-------|--------|
| a | TEST1 |      1 |
| b | TEST2 |      2 |
| c | TEST2 |      3 |
| d | TEST4 |      4 |

DEMO

Answer 2

use the limit clausule, with the offset to choose the row number -1 so if u wanna get the number 8 row so use:

limit 1 offset 7

Answer 3

If you just want a number to come back try this.

create temp sequence temp_seq;
SELECT inline_v1.ROWNUM,inline_v1.c1
FROM
(
select nextval('temp_seq') as ROWNUM, c1 
from sometable
)inline_v1;

You can add a order by to the inline_v1 SQL so your ROWNUM has some sequential meaning to your data.

select nextval('temp_seq') as ROWNUM, c1 
from sometable
ORDER BY c1 desc;

Might not be the fastest, but it's an option if you really do need them.

Answer 4

Postgresql have limit.

Oracle's code:

select *
from
  tbl
where rownum <= 1000;

same in Postgresql's code:

select *
from
  tbl
limit 1000

Answer 5

Postgresql > 8.4

SELECT 
    row_number() OVER (ORDER BY col1) AS i, 
    e.col1, 
    e.col2, 
    ... 
FROM ... 

Answer 6

Postgresql does not have an equivalent of Oracle's ROWNUM. In many cases you can achieve the same result by using LIMIT and OFFSET in your query.