How do I do top 1 in Oracle?

273

votes

How do I do the following?

select top 1 Fname from MyTbl

In Oracle 11g?

sqloracleoracle11ggreatest-n-per-group

Have a look at How does one select the TOP N rows from a table - del.ave

possible duplicate of How do I limit the number of rows returned by an Oracle query after ordering? - Dave Jarvis

Can you tell us the order according to which you want 'top 1'? - Andrew Wolfe

First of all you should never ever rely on the DB engine to do that, ever. If you want to know things like that, put in a sequencer. When you do that it is guaranteed that they will be numbered in the order they were inserted. - FlyingGuy

Very usful material on this topic use-the-index-luke.com/sql/partial-results/top-n-queries - Ilia Maskov

279

votes

If you want just a first selected row, you can:

select fname from MyTbl where rownum = 1

You can also use analytic functions to order and take the top x:

select max(fname) over (rank() order by some_factor) from MyTbl

178

votes

SELECT *
  FROM (SELECT * FROM MyTbl ORDER BY Fname )
 WHERE ROWNUM = 1;

38

votes

With Oracle 12c (June 2013), you are able to use it like the following.

SELECT * FROM   MYTABLE
--ORDER BY COLUMNNAME -OPTIONAL          
OFFSET 0 ROWS FETCH NEXT 1 ROWS ONLY

11

votes

You could use ROW_NUMBER() with a ORDER BY clause in sub-query and use this column in replacement of TOP N. This can be explained step-by-step.

See the below table which have two columns NAME and DT_CREATED.

If you need to take only the first two dates irrespective of NAME, you could use the below query. The logic has been written inside query

-- The number of records can be specified in WHERE clause
SELECT RNO,NAME,DT_CREATED
FROM
(
    -- Generates numbers in a column in sequence in the order of date
    SELECT ROW_NUMBER() OVER (ORDER BY DT_CREATED) AS RNO,
    NAME,DT_CREATED
    FROM DEMOTOP
)TAB
WHERE RNO<3;

RESULT

In some situations, we need to select TOP N results respective to each NAME. In such case we can use PARTITION BY with an ORDER BY clause in sub-query. Refer the below query.

-- The number of records can be specified in WHERE clause
SELECT RNO,NAME,DT_CREATED
FROM
(
  --Generates numbers in a column in sequence in the order of date for each NAME
    SELECT ROW_NUMBER() OVER (PARTITION BY NAME ORDER BY DT_CREATED) AS RNO,
    NAME,DT_CREATED
    FROM DEMOTOP
)TAB
WHERE RNO<3;

RESULT

11

votes

select * from (
    select FName from MyTbl
)
where rownum <= 1;

10

votes

You can do something like

    SELECT *
      FROM (SELECT Fname FROM MyTbl ORDER BY Fname )
 WHERE rownum = 1;

You could also use the analytic functions RANK and/or DENSE_RANK, but ROWNUM is probably the easiest.

6

votes

Use:

SELECT x.*
  FROM (SELECT fname 
          FROM MyTbl) x
 WHERE ROWNUM = 1

If using Oracle9i+, you could look at using analytic functions like ROW_NUMBER() but they won't perform as well as ROWNUM.

3

votes

To select the first row from a table and to select one row from a table are two different tasks and need a different query. There are many possible ways to do so. Four of them are:

First

select  max(Fname) from MyTbl;

Second

select  min(Fname) from MyTbl;

Third

select  Fname from MyTbl  where rownum = 1;

Fourth

select  max(Fname) from MyTbl where rowid=(select  max(rowid) from MyTbl)

3

votes

I had the same issue, and I can fix this with this solution:

select a.*, rownum 
from (select Fname from MyTbl order by Fname DESC) a
where
rownum = 1

You can order your result before to have the first value on top.

Good luck

How do I do top 1 in Oracle?

9 Answers