This question already has answers here:
How do I limit the number of rows returned by an Oracle query after ordering?
(14 answers)
Closed 7 years ago.
I am trying get information of 2 lowest salary holders from default "scott" table.
This is the query I am trying:
SELECT TOP 2 * FROM emp ORDER BY sal ASC
But I'm getting this error:
ORA-00923: FROM keyword not found where expected
Screenshot:
In the most recent versions of Oracle, you can use the ANSI standard:
SELECT emp.*
FROM emp
ORDER BY sal ASC
FETCH FIRST 2 ROWS ONLY;
In older versions:
SELECT e.*
FROM (SELECT emp.*
FROM emp
ORDER BY sal ASC
) e
WHERE rownum <= 2;
You can use ROWNUM in Oracle to get two first rows of your query results.
SELECT EMP1.* FROM (SELECT * FROM EMP ORDER BY SAL ASC) EMP1 WHERE ROWNUM < 3;
TOP X is used by SQL Server
Fetch first is used by Oracle and DB2
(rownum is also available in Oracle)
Limit is used by mysql
Many can also use a windowing function (ROW_NUMBER()) in a sub query.
You want
select * from emp ORDER BY sal ASC
fetch first 2 rows only
Related
This question already has answers here:
How do I limit the number of rows returned by an Oracle query after ordering?
(14 answers)
Closed 2 months ago.
Here's the query
SELECT concat(FIRSTNAME,LASTNAME) AS NAME, HIREDATE from EMPLOYEE ORDER BY HIREDATE
WHERE ROWNUM = 1;
I've been trying to use rownum function but I keep getting the error - "ORA-00933: SQL command not properly ended".
You can try like this:
SELECT *
FROM (SELECT concat(FIRSTNAME,LASTNAME) AS NAME, HIREDATE from EMPLOYEE ORDER BY HIREDATE )
WHERE ROWNUM = 1;
This question already has answers here:
How do I limit the number of rows returned by an Oracle query after ordering?
(14 answers)
Closed 3 years ago.
I am searching for a query to find the details of highest paid employee in the entire organization. I am using oracle DB.
Queries which I tried are:
select * from EMP order by SAL desc FETCH FIRST 1ROW ONLY;
ERROR: SQL command not properly ended
select * from EMP order by SAL desc where rownum = 1;
ERROR: SQL command not properly ended
select * from EMP order by SAL desc LIMIT 0 , 1;
ERROR: SQL command not properly ended
You could use:
SELECT *
FROM (SELECT * FROM emp ORDER BY sal DESC)
WHERE ROWNUM = 1
Please note that if rows have identifical salaries, ROWNUMBER will rank them randomly. To handle ties, you could use RANK() instead (or maybe DENSE_RANK(), depending on your needs):
SELECT *
FROM (
SELECT
e.*,
RANK() OVER(ORDER BY sal DESC) rn
FROM emp
)
WHERE rn = 1
There is an issue with all three statements.
Try this:
select * from EMP order by SAL desc FETCH FIRST ROW ONLY;
or use an analytical function ROW_NUMBER:
SELECT T.* FROM
(SELECT
T.*, ROW_NUMBER() OVER(ORDER BY SAL DESC NULLS LAST) RN
FROM EMP) T
WHERE RN = 1
Cheers!!
This question already has answers here:
How do I limit the number of rows returned by an Oracle query after ordering?
(14 answers)
Closed 5 years ago.
What is wrong with below code?
SELECT first_name, last_name
FROM employees
UNION ALL
SELECT first_name, last_name
FROM dependents
ORDER BY last_name
LIMIT 6 OFFSET 1;
Even a simple query with LIMIT doesn't seem to be working :
SELECT first_name, last_name
FROM dependents
ORDER BY last_name
LIMIT 6 OFFSET 1;
Getting this error repeatedly: ORA-00933: SQL command not properly
ended
I believe oracle does not support LIMIT. Try this
ORDER BY last_name
OFFSET 1 ROWS FETCH NEXT 6 ROWS ONLY;
Note this syntax supports from Oracle 12c
What is wrong with the code is that Oracle does not support limit. Period. The most recent versions support the ANSI standard fetch first <n> rows only.
Perhaps you intend:
SELECT e.*
FROM (SELECT e.*, ROW_NUMBER() OVER (ORDER BY last_name) as seqnum
FROM (SELECT first_name, last_name FROM employees
UNION ALL
SELECT first_name, last_name
FROM dependents
) e
ORDER BY last_name
) e
WHERE seqnum BETWEEN 1 and 7;
I have to get second five (6-10) best salaries records from sorted table using ROWNUM.
Using ROWNUM is necessary.
When I execute query:
SELECT ROWNUM AS position, name, salary
FROM (SELECT name, salary
FROM employees
ORDER BY salary DESC)
WHERE ROWNUM <= 10;
I get a first 10 best records.
And now when I try execute query:
SELECT ROWNUM AS position, name, salary
FROM (SELECT name, salary
FROM employees
ORDER BY salary DESC)
WHERE ROWNUM >= 6 AND ROWNUM <= 10;
I get a empty table. Why doesn't it work?
As explained in the documentation, rownum is evaluated as the rows are fetched. If you never fetch the first row, you never get to the second. Hence, no rows are fetched:
Conditions testing for ROWNUM values greater than a positive integer
are always false. For example, this query returns no rows:
SELECT * FROM employees
WHERE ROWNUM > 1;
But, more importantly, you are using Oracle 12C. So, use fetch first instead of rownum. This has multiple advantages. Besides being standard SQL, you don't need a subquery:
SELECT name, salary
FROM employees
ORDER BY salary DESC
FETCH FIRST 10 ROWS ONLY;
And for your second:
SELECT name, salary
FROM employees
ORDER BY salary DESC
OFFSET 5 ROWS
FETCH FIRST 5 ROWS ONLY;
I write in queston that using ROWNUM is necessary, because it's
academic task.
In such a case use a subquery
SELECT name, salary
FROM (
SELECT name, salary, ROWNUM as my_rownum
FROM employees
ORDER BY salary DESC
)
WHERE my_rownum BETWEEN 6 AND 10
You can use below query and try....
SELECT name,salary from
( SELECT name,salary, DENSE_RANK() OVER (ORDER BY salary DESC) as rn
from employees )
where rn between 6 and 10;
This question already has answers here:
How to get second largest or third largest entry from a table [duplicate]
(12 answers)
SELECTing top N rows without ROWNUM?
(5 answers)
Closed 9 years ago.
I have a employee table in oracle with name,salary and other details.
I am trying to get the second highest salary but not able to fetch.
This one working fine
with e_salary as (select distinct salary from employee)
select salary from e_salary
order by salary desc
And gives output:
450000
61000
60000
50000
40000
30000
20000
6000
but when i am using the same query to fetch second highest row not getting any output
select salary
from ( with e_salary as (select distinct salary from employee)
select salary from e_salary order by salary desc)
where rownum = 2
but as i replace the rownum=2 with rownum<2 it gives output of first two records. Please someone explain why rownum=2 is not working
This will work:
select salary from ( select salary , rownum as rn from (select salary
from e_salary order by salary desc)) where rn = 2;
Why it doesn't work:
When assigning ROWNUM to a row, Oracle starts at 1 and only only increments the value when a row is selected; that is, when all conditions in the WHERE clause are met. Since our condition requires that ROWNUM is greater than 2, no rows are selected and ROWNUM is never incremented beyond 1.
Hope u are clear right now.
select ename ,sal ,rank() over (order by sal desc) ranking from emp;
Try this one.
Follow this link, all the things regarding nth highest row is given over here in oracle:
http://www.oratable.com/nth-highest-salary-in-oracle/
Use of rownum is a tricky affair. Safest bet is to use it only when you want to limit the number of results to be shown. For example rownum<2 or rownum<=5.
Why rownum=2 will not work?
Read here - http://www.oracle.com/technetwork/issue-archive/2006/06-sep/o56asktom-086197.html
In summary, this is how oracle execute a query
The FROM/WHERE clause goes first.
ROWNUM is assigned and incremented to each output row from the FROM/WHERE clause.
SELECT is applied.
GROUP BY is applied.
HAVING is applied.
ORDER BY is applied.
rownum<=2 clause will get converted to
ROWNUM = 1
for x in
( select * from emp )
loop
exit when NOT(ROWNUM <= 2)
OUTPUT record to temp
ROWNUM = ROWNUM+1
end loop
SORT TEMP
if you change exit when NOT(ROWNUM <= 2) with rownnum=2, you can see it will fail in the first run itself
So if I cannot use rownum, what can I use. Try using row_number() http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions137.htm
It works something like
SELECT last_name FROM
(SELECT last_name, ROW_NUMBER() OVER (ORDER BY last_name) R FROM employees)
WHERE R BETWEEN 51 and 100;
rownum in a condition stops evaluating the first time it fails. On the first row returned, rownum is 1, therefore it fails the rownum = 2 test and stops trying. There's an excellent post about it here.
To get the second-highest salary, use the Oracle analytical DENSE_RANK function:
SELECT DISTINCT Salary FROM (
SELECT Salary, DENSE_RANK() OVER (ORDER BY Salary DESC) AS SalaryRank
FROM e_salary)
WHERE SalaryRank = 2
Note that if there's a tie for second, the query could return more than one value. That's why the outer SELECT is a SELECT DISTINCT.
First you should understand what the rownum is. Let me give you an example,
you want to get data with a filter and rownum=2,
first Oracle executes the sql with filter and get the first record,
give it the rownum 1,
and then compare it the rownum filter rownum=2, which doesn't match, so discard record,
then get second record, give it rownum=1(if the first record is matched then the rownum will be 2) too, then do the compare............
So you can find the reason.
Without using rownum command you can get the second highest salary by using this query:
select MAX(Salary) from Employee
WHERE Salary NOT IN
(select MAX(Salary) from Employee )
or,
select MAX(Salary) from Employee
WHERE Salary <>
(select MAX(Salary) from Employee )
query for nth highest:
SELECT * FROM Employee Emp1
WHERE (N-1) =
(SELECT COUNT(DISTINCT(Emp2.Salary))FROM Employee Emp2
WHERE Emp2.Salary > Emp1.Salary)
From what I understand, rownum numbers the rows in a result set.
So, in your example:
select * from table1 where rownum=2
How many rows are there going to be in the result set? Therefore, what rownum would be assigned to such a row? Can you see now why no result is actually returned?
In general, you should avoid relying on rownum, or any features that imply an order to results. Try to think about working with the entire set of results.
With that being said, I believe the following would work:
select * from (select rownum as rn,table1.* from table1) as t where t.rn = 2
Because in that case, you're numbering the rows within the subquery.