I have 3 Tables:
So I need an SQLite query that shows me the Row Number of the s_id=7 ( it must be here 3 )
I search too much on the Internet to find tips but I didn't find! it will be perfect if someone can help me with that.
You can use window functions like this:
select *
from (
select s_id, row_number() over(order by s_id) as rn
from section
) s
where s_id = 7
Or, if your version of SQLite does not support window functions, you can use a subquery:
select s_id,
(select count(*) from section s1 where s1.s_id <= s.id) as rn
from section s
where s_id = 7
Related
I'm trying to get my head around SQL and am using Snowflake as a testbed to do this. I have a table with products which have multiple reviews against them. I am trying to structure a query to only show products with 2 or more reviews and then only show the second review. As I say, this is merely me trying to better understand SQL so selecting the second review is a random ask. The table is made up of 4 columns. 1 is Product ID, 2 is Product Name, 3 is Review and 4 is Date Review was posted.
Thanks in advance for any help.
You use row_number() for this type of query:
select t.*
from (select t.*,
row_number() over (partition by product_id order by date_review asc) as seqnum
from t
) t
where seqnum = 2;
You can use a windowing function like ROW_NUMBER() to make numbered groupings, eg:
WITH Review_Sequence (
SELECT r.*,
ROW_NUMBER() OVER (PARTITION BY Product_ID ORDER BY Review_Date) Review_No
FROM Reviews r
)
SELECT * FROM Review_Sequence WHERE Review_No = 2
I´m using Sqlite3 on a grid application pretty much like that post here..
The grid needs the rows that is being show and the total number of rows found, used for paging.
On Oracle I use the following statement to get rows from 100 to 500 - fields Id, Name, Phone where Deleted=false:
SELECT * FROM (SELECT ROW_NUMBER()
OVER (ORDER BY ID) AS RN,
COUNT(*) OVER (ORDER BY (SELECT NULL) AS CNT)
Id, Name, Phone FROM MyTable WHERE Deleted='F')
T WHERE RN > 100 AND RN < 500;
On MySQl, I normally use the excellet SELECT SQL_CALC_FOUND_ROWS followed by a SELECT FOUND_ROWS() call.
So my questions are:
a) Is there any equivalent of this Sqlite3 for either Oracle or MySQL option above ?
b) How can I accomplish that on Sqlite3 without issuing 2 selects (one for querying and another one for counting) ?
The question posted here does not solve my problem because it does not return the number of records, just pages through the table.
Thanks a lot for helping...
In recent versions of SQLite (3.25.0 and later) there is support for window functions. So you can rewrite your query as follows:
SELECT * FROM (SELECT ROW_NUMBER() OVER (ORDER BY ID) AS RN,
COUNT() OVER () AS CNT,
Id, Name, Phone FROM MyTable WHERE Deleted='F')
T WHERE RN > 100 AND RN < 500;
not sure if there's an elegant way to acheive this:
Data
ID Ver recID (loads more columns of stuff)
1 1 1
2 2 1
3 3 1
4 1 2
5 1 3
6 2 3
So, we have ID as the Primary Key, the Ver as the version and recID as a record ID (an arbitary base ID to tie all the versions together).
So I'd like to select from the following data, rows 3, 4 and 6. i.e. the highest version for a given record ID.
Is there a way to do this with one SQL query? Or would I need to do a SELECT DISTINCT on the record ID, then a seperate query to get the highest value? Or pull the lot into the application and filter from there?
A GROUP BY would be sufficient to get each maximum version for every recID.
SELECT Ver = MAX(Ver), recID
FROM YourTable
GROUP BY
recID
If you also need the corresponding ID, you can wrap this into a subselect
SELECT yt.*
FROM Yourtable yt
INNER JOIN (
SELECT Ver = MAX(Ver), recID
FROM YourTable
GROUP BY
recID
) ytm ON ytm.Ver = yt.Ver AND ytm.recID = yt.RecID
or, depending on the SQL Server version you are using, use ROW_NUMBER
SELECT *
FROM (
SELECT ID, Ver, recID
, rn = ROW_NUMBER() OVER (PARTITION BY recID ORDER BY Ver DESC)
FROM YourTable
) yt
WHERE yt.rn = 1
Getting maximum ver for a given recID is easy. To get the ID, you need to join on a nested query that gets these maximums:
select ID, ver, recID from table x
inner join
(select max(ver) as ver, recID
from table
group by recID) y
on x.ver = y.ver and x.recID = y.recID
You could use a cte with ROW_NUMBER function:
WITH cte AS(
SELECT ID, Ver, recID
, ROW_NUMBER()OVER(PARTITION BY recID ORDER BY Ver DESC)as RowNum
FROM data
)
SELECT ID,Ver,recID FROM cte
WHERE RowNum = 1
straighforward example using a subquery:
SELECT a.*
FROM tab a
WHERE ver = (
SELECT max(ver)
FROM tab b
WHERE b.recId = a.recId
)
(Note: this assumes that the combination of (recId, ver) is unique. Typically there would be a primary key or unique constraint on those columns, in that order, and then that index can be used to optimize this query)
This works on almost all RDBMS-es, although the correlated subquery might not be handled very efficiently (depending on RDBMS). SHould work fine in MS SQL 2008 though.
I was wondering if it would be possible to enumerate returned rows. Not according to any column content but just yielding a sequential integer index. E.g.
select ?, count(*) as usercount from users group by age
would return something along the lines:
1 12
2 78
3 4
4 42
it is for https://data.stackexchange.com/
try:
SELECT
ROW_NUMBER() OVER(ORDER BY age) AS RowNumber
,count(*) as usercount
from users
group by age
If it's Oracle, use rownum.
SELECT SOMETABLE.*, ROWNUM RN
FROM SOMETABLE
WHERE SOMETABLE.SOMECOLUMN = :SOMEVALUE
ORDER BY SOMETABLE.SOMEOTHERCOLUMN;
The final answer will entirely depend on what database you're using.
For MySql:
SELECT #row := #row + 1 as row FROM anytable a, (SELECT #row := 0) r
use rownumber function available in sql server
SELECT
ROW_NUMBER() OVER (ORDER BY columnNAME) AS 'RowNumber',count(*) as usercount
FROM users
How you'd do that depends on your database server. In SQL Server, you could use row_number():
select row_number() over (order by age)
, age
, count(*) as usercount
from users
group by
age
order by
age
But it's often easier and faster to use client side row numbers.
for Mysql
set #row:=0;
select #row:=#row+1 as row, a.* from table_name as a;
In contrast to majority of other answers, and in accordance of the actual OP question, to
enumerate returned rows (...) NOT according to any column content
but rather in the order of returned query, one could use a dummy ordinal variable to ORDER BY in an ROW_NUMBER function, e.g.
ROW_NUMBER() OVER(ORDER BY (SELECT 0)) AS row_num
where one could actually use anything as an argument to the SELECT-statement, like SELECT 100, SELECT ‘A’, SELECT NULL, etc..
This way, the row numbers will be enumerated in the same order the data was added to the table.
I have an SQL Query that i'm running but I only want to select a specific row. For example lets say my query was:
Select * from Comments
Lets say this returns 10 rows, I only want to select the 8th record returned by this query. I know I can do:
Select Top 5 * from Comments
To get the top 5 records of that query but I only want to select a certain record, is there anything I can put into this query to do that (similar to top).
Thanks
jack
This is a classic interview question.
In Ms SQL 2005+ you can use the ROW_NUMBER() keyword and have the Predicate ROW_NUMBER = n
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber = 5;
In SQL2000 you could do something like
SELECT Top 1 *FROM
[tblApplications]
where [ApplicationID] In
(
SELECT TOP 5 [ApplicationID]
FROM [dbo].[tblApplications]
order by applicationId Desc
)
How about
SELECT TOP 1 * FROM
(SELECT TOP 8 * FROM Comments ORDER BY foo ASC)
ORDER BY foo DESC
First, you should say which RDBMS you're using.
Second, you should give careful thought to what it is you're trying to accomplish. Relational Databases are set-based. In general, the order of elements in a set does not matter. You'll want to ask why it matters in this case, then see if there's a better way to embed the concept of order into the query itself.
For instance, in SQL Server 2005 (and other RDBMS), you can use the ROW_NUMBER function to assign a sequential number to each row returned, based on the criteria you specify. You could then select rows based on the row number. Example from Books Online:
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 50 AND 60;
SELECT * FROM comments WHERE ...conditions... LIMIT 1 OFFSET 8
OFFSET is a good thing for MySQL
For SQL Server 2005:
select rank() OVER (ORDER BY c.subject, c.date) as rank, c.subject, c.date
from comments c
where rank = 8
Well, in T-SQL (the dialect for SQL Server) you can do the following:
SELECT TOP 1 *
FROM (SELECT TOP 8 *
FROM Table
ORDER
BY SortField)
ORDER
BY SortField DESC
This way you get the 8th record.
I have read the question & your comments on you would want next 3 blog comments etc.
How is your tables structured?
Assume that you have blog post Id & comment Id is generated in ascending order for each blog post, you could do a SELECT based on the current Id.
e.g. if the blogpostId = 101, you get the top 3 comments order by posted Id. Now lets say, you want to get the next 3 comments - you could do a SELECT WHERE commentId between the last comment id shown TO the comment id - 3
But all that depends on how your tables are defined.
In SQL 2000 where you do not have ROW_NUMBER() function you could use a work-around like this:
SELECT CommentsTableFieldList, IDENTITY(INT, 1,1) as seqNo
INTO #SeqComments
FROM Comments
SELECT * FROM #SeqComments
WHERE seqNo = 8
select top 1 *
from TableName
where ColumnName1 in
(
select top nth ColumnName1
from TableName
order by ColumnName1 desc
)
order by ColumnName1 desc
From the SELECT reference, use the LIMIT keyword:
SELECT * FROM tbl LIMIT 5,10; # Retrieve rows 6-15
SELECT * FROM tbl LIMIT 5; # Retrieve first 5 rows
Note: this is for MySQL, other SQL engines may have a different keyword.
Select from tablename limit nthrow,1;
try This
Let us assume , We want select 5th row of WC_Video Table
And
Select * from (Select Row_Number() over (Order by Uploadedon) as 'rownumber',* from Wc_Video )as Temp where rownumber=5