Related
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 need to get maximum number from a part of the value that generally start with year followed by slash(/). So I need a maximum number after the slash(/) but year should be 2016
2016/422
2016/423
2016/469
2016/0470
2014/777
2015/123
2015/989
I tried this query
SELECT columname FROM tablename WHERE columname LIKE '2016/%' ORDER BY id DESC
the above query always giving '2016/469' as first record, how to get '2016/0470' as the maximum number?
any help will be much appreciated.
Thank you.
If columname follows that pattern YEAR/0000, you can use SUBSTRING function from MySQL to remove the part of the string you don't want.
SELECT value FROM (
SELECT CAST(SUBSTRING(columname, 0, 4) AS UNSIGNED) as year, CAST(SUBSTRING(columname FROM 6) AS UNSIGNED) as value FROM tablename
) total
ORDER BY year DESC, value DESC
LIMIT 1;
You need to split the string into 2 parts and evaluate them as numbers, instead of strings. The following formula will return the number after the / in the fieldname. All functions used below are described in the string functions section of the MySQL documentation. This way you can get the number after the / character, even if it is not year before the /, but sg else. The + 0 converts the string to a number, eliminating any leading 0.
select right(columnname, char_length(columnname)-locate('/',columnname)) + 0
from tablename
Just take the max() of the above expression to get the expected results.
UPDATE:
If you need the original number and the result has to be restricted to a specific year, then you need to join back the results to the original table:
select columnname
from tablename t1
inner join (select max(right(t.columnname, char_length(t.columnname)-locate('/',t.columnname)) + 0) as max_num
from tablename t
where left(t.columnname,4)='2016'
) t2
on right(t1.columnname, char_length(1t.columnname)-locate('/',t1.columnname)) + 0 = t2.max_num
where left(t1.columnname,4)='2016'
There are lots of suggestions given as answers already. But some of those seem overkill to me.
Seems like the only change needed to the OP query is the expression in the ORDER BY clause.
Instead of:
ORDER BY id
We just need to order by the numeric value following the slash. And there are several approaches, several expressions, that will get that from the example data.
Since the query already includes a condition columname LIKE '2016/%'
We can get the characters after the first five characters, and then convert that string to a numeric value by adding zero.
ORDER BY SUBSTRING(columname,6) + 0 DESC
If we only want to return one row, add
LIMIT 1
http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_substring
If we only want to return the numeric value, we could use the same expression in the SELECT list, in addition columnname.
This isn't the only approach. There are lots of other approaches that will work, and don't use SUBSTRING.
Try like this:
SELECT
MAX(CAST(SUBSTRING(t.name,
LOCATE('/', t.name) + 1)
AS UNSIGNED)) AS max_value
FROM
tablename AS t;
You can try with this little uggly approach:
SELECT t.id, t2.secondNumber FROM table AS t
JOIN (SELECT id,
CONCAT(SUBSTRING(field,1,5),
if(SUBSTRING(SUBSTRING(field, 6),1,1)='0',
SUBSTRING(field, 6),
SUBSTRING(field,7)
)
) as secondNumber FROM table ) AS t2 ON t2.id=t.id
ORDER BY t2.secondNumber DESC
Would be valid only if the 0 (zeroes) before the second number (after the slash) are no more than 1.
Or if the year doesn`t matter you can try to order them only by the second number if it is ok:
SELECT t.id, t2.secondNumber FROM table AS t
JOIN (SELECT id,
if(SUBSTRING(SUBSTRING(field, 6),1,1)='0',
SUBSTRING(field, 6),
SUBSTRING(field,7)
) as secondNumber FROM table ) AS t2 ON t2.id=t.id
ORDER BY t2.secondNumber DESC
I am trying to optimize following query.
SELECT t3.*,
(SELECT SUM(t4.col_sum)
FROM (...) t4
WHERE t4.timestamp BETWEEN CONCAT(SUBSTR(t3.timestamp, 1, 11), "00:00:00") AND t3.timestamp)
AS cum_sum
FROM (...) t3
Where (...) is a container for long query. It results 2 columns: timestamp and col_sum. I want to add third column to it by writing a query. That third column is a cumulative sum of col_sum.
The problem is I am putting same big query in two places (...)
Is there a way I can obtain a result and use the result in those two/multiple places (...)?
One method is to use a temporary table.
Probably a more efficient method is to use variables to calculate a cumulative sum. It would be something like:
select t.*,
(#c := if(#t = left(t.timestamp, 11), #c + t.col_sum,
if(#t := left(t.timestamp, 11), 0, 0)
)
) as cumesum
from (. . .) t cross join
(select #t := '', #c := 0) vars
order by t.timestamp;
The above query orders the rows by timestamp. The variable #t keeps track of the first 11 characters in the timestamp -- as I read your logic, you want to do the cumulative sum only within a group where this is constant.
The variable #c keeps track of the cumulative sum, resetting to zero when a new "first 11 characters" are encountered. The logic looks a bit complicated, but it is best to put all variable assignments in a single expression, because MySQL does not guarantee the order of evaluation of expressions.
I have a table of student scorecard.
here is the table,
subject | mark1 | mark2 | mark3 |......|markn
stud1 | 99 | 87 | 92 | | 46
stud2 |....................................
.
.
studn |....................................|
Now, I need to sum it for each student of total marks. I got it by using sum(mark1+mark2+...+markn) group by stud. I want to know how to sum it without adding each column name,it will be huge when in case up to marks26. so could anyone know how to fix it.
SELECT student, (SUM(mark1)+SUM(mark2)+SUM(mark3)....+SUM(markn)) AS Total
FROM your_table
GROUP BY student
Another way of doing this is by generating the select query. Play with this fiddle.
SELECT CONCAT('SELECT ', group_concat(`COLUMN_NAME` SEPARATOR '+'), ' FROM scorecard')
FROM `INFORMATION_SCHEMA`.`COLUMNS`
WHERE `TABLE_SCHEMA` = (select database())
AND `TABLE_NAME` = 'scorecard'
AND `COLUMN_NAME` LIKE 'mark%';
The query above will generate another query that will do the selecting for you.
Run the above query.
Get the result and run that resulting query.
Sample result:
SELECT mark1+mark2+mark3 FROM scorecard
You won't have to manually add all the columns anymore.
If any of your markn columns are "AllowNull" then you will need to do a little extra to insure the correct result is returned, this is because 1 NULL value will result in a NULL total.
This is what i would consider to be the correct answer.
SUM(IFNULL(`mark1`, 0) + IFNULL(`mark2`, 0) + IFNULL(`mark3`, 0)) AS `total_marks`
IFNULL will return the 2nd parameter if the 1st is NULL.
COALESCE could be used but i prefer to only use it if it is required.
See What is the difference bewteen ifnull and coalesce in mysql?
SUM-ing the entire calculation is tidier than SUM-ing each column individually.
SELECT `student`, SUM(IFNULL(`mark1`, 0) + IFNULL(`mark2`, 0) + IFNULL(`mark3`, 0)) AS `total_marks`
FROM student_scorecard
GROUP BY `student`
i want to know how to sum it without adding each column name,it will be huge when in case up to marks26
To generate and execute this statement dynamically in sql you would need to use the INFORMATION_SCHEMA.COLUMNS table to create a query string then execute it using a prepared statement saved in a variable.
SELECT CONCAT('SELECT `student`, SUM(IFNULL(`', group_concat(`COLUMN_NAME` SEPARATOR '`, 0) + IFNULL(`'), '`, 0) AS `total_marks` FROM `student_scorecard` GROUP BY `student`')
FROM `INFORMATION_SCHEMA`.`COLUMNS`
WHERE `TABLE_SCHEMA` = (select DATABASE())
AND `TABLE_NAME` = 'student_scorecard'
AND `COLUMN_NAME` LIKE 'mark%'
# adapted from https://stackoverflow.com/a/22369767/2273611
# insert statement sql into a variable
INTO #statement_var;
#prepare the statement string
PREPARE stmt_name FROM #statement_var;
#execute the prepared statement/query
EXECUTE stmt_name;
# release statement
DEALLOCATE PREPARE stmt_name;
SELECT student, SUM(mark1+mark2+mark3+....+markn) AS Total FROM your_table
The short answer is there's no great way to do this given the design you have. Here's a related question on the topic: Sum values of a single row?
If you normalized your schema and created a separate table called "Marks" which had a subject_id and a mark column this would allow you to take advantage of the SUM function as intended by a relational model.
Then your query would be
SELECT subject, SUM(mark) total
FROM Subjects s
INNER JOIN Marks m ON m.subject_id = s.id
GROUP BY s.id
//Mysql sum of multiple rows
Hi Here is the simple way to do sum of columns
SELECT sum(IF(day_1 = 1,1,0)+IF(day_3 = 1,1,0)++IF(day_4 = 1,1,0)) from attendence WHERE class_period_id='1' and student_id='1'
You could change the database structure such that all subject rows become a column variable (like spreadsheet). This makes such analysis much easier
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