Sqlite get max id not working (?) - sql

Im using this:
SELECT *
WHERE id=MAX(id)
FROM history;
But my query is empty. I have also tried this (This one works):
SELECT MAX(id) AS max_id
FROM history;
But obviusly my query only contains the max_id key. What am I doing wrong with the first one?


You need to add another level of select for the MAX, like this:
SELECT *
WHERE id=(SELECT MAX(id) from history)
FROM history;
A better approach would be to order by id in descending order, and limit the output to a single row:
SELECT *
FROM history
ORDER BY id DESC
LIMIT 1


Actually most simple query to get the max value of a column in sqlite is:
select MAX(id) from table;


SELECT top 1
FROM history
ORDER BY id DESC

Related

Fetch first 5 and last 5 records through a single statement

I am working on python sqlite3.
This statement gets records 5 - 14;
SELECT * FROM something LIMIT 5, 10;
But how do I get, lets say the first five and last five records through a single statement?

You can combine output of two select statement like this:
(SELECT * FROM `something` order by some_column_name
limit 0,5)
union
(SELECT * FROM `something` order by some_column_name desc
limit 0,5
)
Specify some ordering of rows, so that it will select rows accordingly.

Maybe the better way is using rowid in your order by clause to get the first and last rows based on inserting the rows:
select test from
(select test,rowid from table1 order by rowid asc limit 0,5)t1
union all
select test from
(select test,rowid from table1 order by rowid desc limit 0,5)t2;
Here is a sample in SQL Fiddle

Select entire row based on a max value of a field - without nesting

select *
from webOrders
where lastModifiedDate in (select max (lastModifiedDate) from webOrders)
Is there a simpler way without nesting the selects?
Doing something like this also results in an error:
select id, amount, quantity, max(lastModifiedDate) from webOrders.

There are a couple of approaches, depending on your needs.
If you only need one row returned, you can sort on the column of interest and return the top row. For example:
select top 1 *
from `order`
order by last_modified_date desc
if you use SQL Server or
select *
from `order`
order by last_modified_date desc
limit 1
if you use MySQL.
If you need to get one row per group, then you do typically have to use a subquery or a join.

select TOP 1 * from [order] order by lastModifiedDate desc

You can do select
SELECT TOP 1 * FROM XXX
http://www.w3schools.com/sql/sql_top.asp

how do i select the last 10 records added?

i am running mysql and i would like to display the last 10 records that were added. what is the select statement for this?

If you have an auto-incrementing ID, you can do this:
SELECT * FROM my_table ORDER BY id DESC LIMIT 10;
If you don't, you'll need some criteria you can order by. An insertion date or something. The LIMIT 10 clause is what you're looking for here.

If you have an autoincrementing ID you can use this:
SELECT *
FROM yourtable
ORDER BY id DESC
LIMIT 10
If you have a column added_datetime that is set to the time of the insert then you can use that instead:
SELECT *
FROM yourtable
ORDER BY added_datetime DESC
LIMIT 10

How to select a random record from a MySQL database?

I am using the following query to select 1 random record -
SELECT name FROM table WHERE id >= (SELECT FLOOR( MAX(id) * RAND()) FROM table ) ORDER BY id LIMIT 1
but it gives me the same set of records every time I call it. How do I get better random record?

Try this:
SELECT * FROM tableName ORDER BY RAND() LIMIT 1

Selecting Nth Record in an SQL Query

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