How do I do top 1 in Oracle?

Question

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

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

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

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

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

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.

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.