I'm interested in learning some (ideally) database agnostic ways of selecting the nth row from a database table. It would also be interesting to see how this can be achieved using the native functionality of the following databases:
SQL Server
MySQL
PostgreSQL
SQLite
Oracle
I am currently doing something like the following in SQL Server 2005, but I'd be interested in seeing other's more agnostic approaches:
WITH Ordered AS (
SELECT ROW_NUMBER() OVER (ORDER BY OrderID) AS RowNumber, OrderID, OrderDate
FROM Orders)
SELECT *
FROM Ordered
WHERE RowNumber = 1000000
Credit for the above SQL: Firoz Ansari's Weblog
Update: See Troels Arvin's answer regarding the SQL standard. Troels, have you got any links we can cite?
There are ways of doing this in optional parts of the standard, but a lot of databases support their own way of doing it.
A really good site that talks about this and other things is http://troels.arvin.dk/db/rdbms/#select-limit.
Basically, PostgreSQL and MySQL supports the non-standard:
SELECT...
LIMIT y OFFSET x
Oracle, DB2 and MSSQL supports the standard windowing functions:
SELECT * FROM (
SELECT
ROW_NUMBER() OVER (ORDER BY key ASC) AS rownumber,
columns
FROM tablename
) AS foo
WHERE rownumber <= n
(which I just copied from the site linked above since I never use those DBs)
Update: As of PostgreSQL 8.4 the standard windowing functions are supported, so expect the second example to work for PostgreSQL as well.
Update: SQLite added window functions support in version 3.25.0 on 2018-09-15 so both forms also work in SQLite.
PostgreSQL supports windowing functions as defined by the SQL standard, but they're awkward, so most people use (the non-standard) LIMIT / OFFSET:
SELECT
*
FROM
mytable
ORDER BY
somefield
LIMIT 1 OFFSET 20;
This example selects the 21st row. OFFSET 20 is telling Postgres to skip the first 20 records. If you don't specify an ORDER BY clause, there's no guarantee which record you will get back, which is rarely useful.
I'm not sure about any of the rest, but I know SQLite and MySQL don't have any "default" row ordering. In those two dialects, at least, the following snippet grabs the 15th entry from the_table, sorting by the date/time it was added:
SELECT *
FROM the_table
ORDER BY added DESC
LIMIT 1,15
(of course, you'd need to have an added DATETIME field, and set it to the date/time that entry was added...)
SQL 2005 and above has this feature built-in. Use the ROW_NUMBER() function. It is excellent for web-pages with a << Prev and Next >> style browsing:
Syntax:
SELECT
*
FROM
(
SELECT
ROW_NUMBER () OVER (ORDER BY MyColumnToOrderBy) AS RowNum,
*
FROM
Table_1
) sub
WHERE
RowNum = 23
I suspect this is wildly inefficient but is quite a simple approach, which worked on a small dataset that I tried it on.
select top 1 field
from table
where field in (select top 5 field from table order by field asc)
order by field desc
This would get the 5th item, change the second top number to get a different nth item
SQL server only (I think) but should work on older versions that do not support ROW_NUMBER().
Verify it on SQL Server:
Select top 10 * From emp
EXCEPT
Select top 9 * From emp
This will give you 10th ROW of emp table!
Contrary to what some of the answers claim, the SQL standard is not silent regarding this subject.
Since SQL:2003, you have been able to use "window functions" to skip rows and limit result sets.
And in SQL:2008, a slightly simpler approach had been added, using
OFFSET skip ROWS
FETCH FIRST n ROWS ONLY
Personally, I don't think that SQL:2008's addition was really needed, so if I were ISO, I would have kept it out of an already rather large standard.
1 small change: n-1 instead of n.
select *
from thetable
limit n-1, 1
SQL SERVER
Select n' th record from top
SELECT * FROM (
SELECT
ID, NAME, ROW_NUMBER() OVER(ORDER BY ID) AS ROW
FROM TABLE
) AS TMP
WHERE ROW = n
select n' th record from bottom
SELECT * FROM (
SELECT
ID, NAME, ROW_NUMBER() OVER(ORDER BY ID DESC) AS ROW
FROM TABLE
) AS TMP
WHERE ROW = n
When we used to work in MSSQL 2000, we did what we called the "triple-flip":
EDITED
DECLARE #InnerPageSize int
DECLARE #OuterPageSize int
DECLARE #Count int
SELECT #Count = COUNT(<column>) FROM <TABLE>
SET #InnerPageSize = #PageNum * #PageSize
SET #OuterPageSize = #Count - ((#PageNum - 1) * #PageSize)
IF (#OuterPageSize < 0)
SET #OuterPageSize = 0
ELSE IF (#OuterPageSize > #PageSize)
SET #OuterPageSize = #PageSize
DECLARE #sql NVARCHAR(8000)
SET #sql = 'SELECT * FROM
(
SELECT TOP ' + CAST(#OuterPageSize AS nvarchar(5)) + ' * FROM
(
SELECT TOP ' + CAST(#InnerPageSize AS nvarchar(5)) + ' * FROM <TABLE> ORDER BY <column> ASC
) AS t1 ORDER BY <column> DESC
) AS t2 ORDER BY <column> ASC'
PRINT #sql
EXECUTE sp_executesql #sql
It wasn't elegant, and it wasn't fast, but it worked.
In Oracle 12c, You may use OFFSET..FETCH..ROWS option with ORDER BY
For example, to get the 3rd record from top:
SELECT *
FROM sometable
ORDER BY column_name
OFFSET 2 ROWS FETCH NEXT 1 ROWS ONLY;
Here is a fast solution of your confusion.
SELECT * FROM table ORDER BY `id` DESC LIMIT N, 1
Here You may get Last row by Filling N=0, Second last by N=1, Fourth Last By Filling N=3 and so on.
This is very common question over the interview and this is Very simple ans of it.
Further If you want Amount, ID or some Numeric Sorting Order than u may go for CAST function in MySQL.
SELECT DISTINCT (`amount`)
FROM cart
ORDER BY CAST( `amount` AS SIGNED ) DESC
LIMIT 4 , 1
Here By filling N = 4 You will be able to get Fifth Last Record of Highest Amount from CART table. You can fit your field and table name and come up with solution.
ADD:
LIMIT n,1
That will limit the results to one result starting at result n.
Oracle:
select * from (select foo from bar order by foo) where ROWNUM = x
For example, if you want to select every 10th row in MSSQL, you can use;
SELECT * FROM (
SELECT
ROW_NUMBER() OVER (ORDER BY ColumnName1 ASC) AS rownumber, ColumnName1, ColumnName2
FROM TableName
) AS foo
WHERE rownumber % 10 = 0
Just take the MOD and change number 10 here any number you want.
For SQL Server, a generic way to go by row number is as such:
SET ROWCOUNT #row --#row = the row number you wish to work on.
For Example:
set rowcount 20 --sets row to 20th row
select meat, cheese from dbo.sandwich --select columns from table at 20th row
set rowcount 0 --sets rowcount back to all rows
This will return the 20th row's information. Be sure to put in the rowcount 0 afterward.
Here's a generic version of a sproc I recently wrote for Oracle that allows for dynamic paging/sorting - HTH
-- p_LowerBound = first row # in the returned set; if second page of 10 rows,
-- this would be 11 (-1 for unbounded/not set)
-- p_UpperBound = last row # in the returned set; if second page of 10 rows,
-- this would be 20 (-1 for unbounded/not set)
OPEN o_Cursor FOR
SELECT * FROM (
SELECT
Column1,
Column2
rownum AS rn
FROM
(
SELECT
tbl.Column1,
tbl.column2
FROM MyTable tbl
WHERE
tbl.Column1 = p_PKParam OR
tbl.Column1 = -1
ORDER BY
DECODE(p_sortOrder, 'A', DECODE(p_sortColumn, 1, Column1, 'X'),'X'),
DECODE(p_sortOrder, 'D', DECODE(p_sortColumn, 1, Column1, 'X'),'X') DESC,
DECODE(p_sortOrder, 'A', DECODE(p_sortColumn, 2, Column2, sysdate),sysdate),
DECODE(p_sortOrder, 'D', DECODE(p_sortColumn, 2, Column2, sysdate),sysdate) DESC
))
WHERE
(rn >= p_lowerBound OR p_lowerBound = -1) AND
(rn <= p_upperBound OR p_upperBound = -1);
But really, isn't all this really just parlor tricks for good database design in the first place? The few times I needed functionality like this it was for a simple one off query to make a quick report. For any real work, using tricks like these is inviting trouble. If selecting a particular row is needed then just have a column with a sequential value and be done with it.
Nothing fancy, no special functions, in case you use Caché like I do...
SELECT TOP 1 * FROM (
SELECT TOP n * FROM <table>
ORDER BY ID Desc
)
ORDER BY ID ASC
Given that you have an ID column or a datestamp column you can trust.
For SQL server, the following will return the first row from giving table.
declare #rowNumber int = 1;
select TOP(#rowNumber) * from [dbo].[someTable];
EXCEPT
select TOP(#rowNumber - 1) * from [dbo].[someTable];
You can loop through the values with something like this:
WHILE #constVar > 0
BEGIN
declare #rowNumber int = #consVar;
select TOP(#rowNumber) * from [dbo].[someTable];
EXCEPT
select TOP(#rowNumber - 1) * from [dbo].[someTable];
SET #constVar = #constVar - 1;
END;
LIMIT n,1 doesn't work in MS SQL Server. I think it's just about the only major database that doesn't support that syntax. To be fair, it isn't part of the SQL standard, although it is so widely supported that it should be. In everything except SQL server LIMIT works great. For SQL server, I haven't been able to find an elegant solution.
In Sybase SQL Anywhere:
SELECT TOP 1 START AT n * from table ORDER BY whatever
Don't forget the ORDER BY or it's meaningless.
T-SQL - Selecting N'th RecordNumber from a Table
select * from
(select row_number() over (order by Rand() desc) as Rno,* from TableName) T where T.Rno = RecordNumber
Where RecordNumber --> Record Number to Select
TableName --> To be Replaced with your Table Name
For e.g. to select 5 th record from a table Employee, your query should be
select * from
(select row_number() over (order by Rand() desc) as Rno,* from Employee) T where T.Rno = 5
SELECT
top 1 *
FROM
table_name
WHERE
column_name IN (
SELECT
top N column_name
FROM
TABLE
ORDER BY
column_name
)
ORDER BY
column_name DESC
I've written this query for finding Nth row.
Example with this query would be
SELECT
top 1 *
FROM
Employee
WHERE
emp_id IN (
SELECT
top 7 emp_id
FROM
Employee
ORDER BY
emp_id
)
ORDER BY
emp_id DESC
I'm a bit late to the party here but I have done this without the need for windowing or using
WHERE x IN (...)
SELECT TOP 1
--select the value needed from t1
[col2]
FROM
(
SELECT TOP 2 --the Nth row, alter this to taste
UE2.[col1],
UE2.[col2],
UE2.[date],
UE2.[time],
UE2.[UID]
FROM
[table1] AS UE2
WHERE
UE2.[col1] = ID --this is a subquery
AND
UE2.[col2] IS NOT NULL
ORDER BY
UE2.[date] DESC, UE2.[time] DESC --sorting by date and time newest first
) AS t1
ORDER BY t1.[date] ASC, t1.[time] ASC --this reverses the order of the sort in t1
It seems to work fairly fast although to be fair I only have around 500 rows of data
This works in MSSQL
SELECT * FROM emp a
WHERE n = (
SELECT COUNT( _rowid)
FROM emp b
WHERE a. _rowid >= b. _rowid
);
unbelievable that you can find a SQL engine executing this one ...
WITH sentence AS
(SELECT
stuff,
row = ROW_NUMBER() OVER (ORDER BY Id)
FROM
SentenceType
)
SELECT
sen.stuff
FROM sentence sen
WHERE sen.row = (ABS(CHECKSUM(NEWID())) % 100) + 1
select * from
(select * from ordered order by order_id limit 100) x order by
x.order_id desc limit 1;
First select top 100 rows by ordering in ascending and then select last row by ordering in descending and limit to 1. However this is a very expensive statement as it access the data twice.
It seems to me that, to be efficient, you need to 1) generate a random number between 0 and one less than the number of database records, and 2) be able to select the row at that position. Unfortunately, different databases have different random number generators and different ways to select a row at a position in a result set - usually you specify how many rows to skip and how many rows you want, but it's done differently for different databases. Here is something that works for me in SQLite:
select *
from Table
limit abs(random()) % (select count(*) from Words), 1;
It does depend on being able to use a subquery in the limit clause (which in SQLite is LIMIT <recs to skip>,<recs to take>) Selecting the number of records in a table should be particularly efficient, being part of the database's meta data, but that depends on the database's implementation. Also, I don't know if the query will actually build the result set before retrieving the Nth record, but I would hope that it doesn't need to. Note that I'm not specifying an "order by" clause. It might be better to "order by" something like the primary key, which will have an index - getting the Nth record from an index might be faster if the database can't get the Nth record from the database itself without building the result set.
Most suitable answer I have seen on this article for sql server
WITH myTableWithRows AS (
SELECT (ROW_NUMBER() OVER (ORDER BY myTable.SomeField)) as row,*
FROM myTable)
SELECT * FROM myTableWithRows WHERE row = 3
I've got a query that is returning a set of rows. I want to LIMIT what actually gets returned to some subset of these rows by range, relative either to the beginning or end of the range. I can do this easily if the range is only relative to the beginning. For instance, if I want to return rows 5-7 I can do:
SELECT * FROM <table> WHERE <condition> ORDER BY rowid ASC LIMIT 5,2
The only translation I need to do is from (index0,index1) to offset,length where offset=index0 and length=index1-index0.
But I also am trying to allow the range to be specified relative to the end of the range in a single query, i.e. without running a query first to determine the number of rows and then a second query based on this information. So for example if I specify a row range of (-5,-1) this means that I want the last five rows returned. I cannot pass a negative value to LIMIT.
In reading similar questions, one proposed solution seemed to be to change the ORDER of the query. So I suppose I could do:
SELECT * FROM <table> WHERE <condition> ORDER BY rowid DESC LIMIT 1,5
Now I have two problems. First, the returned set is in the wrong order, I still want it return in ascending order. So now I have to have a subquery to reorder everything:
SELECT * FROM (SELECT * FROM <table> WHERE <condition> ORDER BY rowid DESC LIMIT 1,5) AS x ORDER BY x.rowid ASC;
I'm not sure if there is a better way to do it than that, but there is a second issue: this does not work if the starting and ending part of the range are mixed as to what they are relative to. Suppose I want to return the range (10,-2) which is all rows from the tenth to the next to last. In this case, neither of the above approaches will work.
I also saw where the function mysql_num_rows() was mentioned although it did not give example SQL of how to use it.
SELECT * FROM <table> WHERE <condition> ORDER BY rowid DESC LIMIT 10,mysql_num_rows()-2;
But when I try to run this query, I get this error:
ERROR 1327 (42000): Undeclared variable: mysql_num_rows
What about reversing your approach? Asking for rows in range (10, -2) means "everything except first nine rows and last one".
You can translate it into
select * from yourTable order by rowid asc
minus
select * fom yourTable order by rowid asc limit 9
minus
select * fom yourTable order by rowid desc limit 1
Edit
Since MySQL does not support MINUS, the query above could be rewritten using left join instead
select t1.*
from yourTable t1
left join
(select rowid fom yourTable order by rowid asc limit 9) t2
on t1.rowid = t2.rowid
left join
(select rowid fom yourTable order by rowid desc limit 1) t3
on t1.rowid = t3.id
where t2.rowid is null and t3.rowid is null
order by t1.rowid asc
This is based on a different answer that was given to this question, which used MINUS. Unfortunately, MySQL does not support this operator. I used NOT IN instead, and furthermore I had to wrap my query inside additional queries to avoid the MySQL issue of lack of support for LIMIT being in an IN sub-query.
So the premise of the solution as provided by the other answer is to treat a positive starting index and a negative ending indexes as a different case from both indicies negative or positive. Then, select everything but exclude the range at the start and finish. The actual code that MySQL likes and which works for the example range of (10,-2) is:
SELECT *
FROM <table>
WHERE <conditions>
AND rowid NOT IN
(
SELECT * FROM (
SELECT rowid FROM <table> WHERE <conditions> ORDER BY rowid ASC LIMIT 9
)
)
AND rowid NOT IN
(
SELECT * FROM (
SELECT rowid FROM <table> WHERE <conditions> ORDER BY rowid DESC LIMIT 1
)
)
Or more generally, for the range (i0,i1) where i0>=0 and i1<0, replace 9 with i0-1 and 1 with -i1-1. Of course, if either of these values are less than one, that portion of the query can be excluded.
I want to limit selected all except 1st row.
Id is int, but not UNIQUE,
checkIn is date
SELECT * FROM table
Order by property_id, checkIn DESC
LIMIT 2, (SELECT Count(property_id)-1 FROM table)
Both Queries are working. but then I put them together i get
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(SELECT Count(property_id) FROM table)' at line 1
Maybe here is universal key for all rows at LIMIT 1, ALL ?
If you need all rows except the first one, try this:
SELECT * FROM TBL LIMIT 1, 18446744073709551615;
18446744073709551615 is the recommend as a value as in the mysql docs and the maximum of a unsigned bigint.
There was a similar question.
For completeness, here's how you can do it with a prepared statement:
SET #skip=1;
SET #numrows=(SELECT Count(property_id)-1 FROM table);
PREPARE STMT FROM 'SELECT * FROM table Order by property_id, checkIn DESC LIMIT ?, ?';
EXECUTE STMT USING #skip, #numrows;
Although, if it's a InnoDB table, I wouldn't recommend to do a SELECT COUNT(*) on it repeatedly. Unlike MyISAM it doesn't store a row count in the table. Therefore counting on InnoDB can be slow when it has lots of rows.
P.S.: Note, that you have to use limit 1, how_many instead of limit 2, how_many when you want to skip one row, since it starts counting from 0, not from 1.
Johan already mentioned here
You can not use a subquery as a LIMIT argument. Limit argument
should be an INTEGER. You subquery returns, wel... basically, a
table.
From the MySQL manual
The LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants, with these exceptions:
Within prepared statements, LIMIT parameters can be specified using ? placeholder markers.
Within stored programs, LIMIT parameters can be specified using integer-valued routine parameters or local variables as of MySQL 5.5.6.
Edit
Try like this
but i'm not tested
DECLARE offset bigint;
SELECT Count(property_id)-1 INTO offset FROM table;
SELECT * FROM table Order by property_id, checkIn DESC LIMIT 2,offset;
I agree with #omeinusch's answer, but also offer the following alternative:
SELECT * FROM table t JOIN (
SELECT property_id, checkIn
FROM table
ORDER BY property_id, checkIn DESC
LIMIT 2,1
) s ON (t.property_id > s.property_id)
OR (t.property_id = s.property_id AND t.checkIn <= s.checkIn)
If you have a unique id column, then you could do this:
select * FROM table
where id <> (SELECT id FROM table Order by property_id, checkIn DESC LIMIT 1)
Otherwise, assuming property_id and checkIn are unique,
select * FROM table
where concat(property_id,'|',checkIn) <>
(SELECT concat(property_id,'|',checkIn) FROM table Order by property_id, checkIn DESC LIMIT 1)
I'm using the top query for my table but facing the error
You have an error in your sql syntax, chekck the manual that
corresponds to your mysql server version for the right sytntax to use
near '4 * from sitemain order by siteid desc limit 0,30' at line 1
here is the code which i used
SELECT top 4 *
FROM sitemain
ORDER BY siteid DESC
You are mixing MySQL and TSQL syntax together. The query obviously is MySQL (from the error message). What you want is
SELECT * FROM sitemain ORDER BY siteid DESC LIMIT 0,4
What you loking for is actually LIMIT Clause,
The LIMIT clause can be used to constrain the number of rows returned
by the SELECT statement. LIMIT takes one or two numeric arguments,
which must both be nonnegative integer constants (except when using
prepared statements).
With two arguments, the first argument specifies the offset of the
first row to return, and the second specifies the maximum number of
rows to return. The offset of the initial row is 0 (not 1):
Documentation:
https://dev.mysql.com/doc/refman/5.0/en/select.html
SELECT *
FROM sitemain
ORDER BY siteid DESC
LIMIT 4
SELECT *
FROM sitemain
ORDER BY siteid DESC
LIMIT 4
With MySQL you need to use the LIMIT command as explained here:
Limit is used to limit your MySQL query results to those that fall within a specified range. You can use it to show the first X number of results, or to show a range from X - Y results. It is phrased as Limit X, Y and included at the end of your query. X is the starting point (remember the first record is 0) and Y is the duration (how many records to display).
SELECT *
FROM sitemain
ORDER BY siteid DESC
LIMIT 4