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Get the last record from a Microsoft SQL database table using ASP.net (VB) onto a web form.
I'm assuming he's trying to retrieve the last inserted record. As Ariel pointed out, the question is rather ambiguous.
SELECT TOP 1 * FROM Table ORDER BY ID DESC
If you have an identity column called ID, this is easiest. If you don't have an identity PK column for example a GUID you wont be able to do this.
Here is a basic solution:
var order = (from i in db.orders
where i.costumer_id.ToString() == Session["costumer_id"]
orderby i.order_id descending
select i).Take(1).SingleOrDefault();
You need to be more specific with actually putting it onto a web form, but the SQL to get the last record is:
SELECT *
FROM TABLE_NAME
WHERE ID = (SELECT MAX(ID) FROM TABLE_NAME)
Where ID is your ID and TABLE_NAME is your table name.
Related
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I have a table in my app
CREATE TABLE VisitDetails (VisitId INTEGER, UserId TEXT, VisitNumber
TEXT, JobId INTEGER, JobNumber TEXT, StatusId INTEGER, Status TEXT,
SignatureRequired BOOL, StatusDate TIMESTAMP DEFAULT CURRENT_TIMESTAMP
,StartDate TIMESTAMP DEFAULT CURRENT_TIMESTAMP, EndDate TIMESTAMP
DEFAULT CURRENT_TIMESTAMP, IsPPMJob BOOL)
and it was working fine but now I need to alter this table to make already existing column 'VisitId' to become the primary key. Can somebody help me please? It might work by adding Unique constraint to VisitId column of the table but I am trying to put some efficient solution !
You can't change SQLite tables field's primary key once the table is created,
Possible solution is,
Create new table with desired primary key
Copy all data
Drop old table
Here is the documentation link : https://www.sqlite.org/omitted.html
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I have new data coming into the app all the time, so I want to limit the number of rows in a table to, say, 100 records. I would describe it as a FIFO queue. Whenever there new data (just a few rows a time) coming in, old data at the 'bottom' of the table are flushed out and deleted. Since it's FIFO, I don't want to manually perform a sort, then delete, then insert back in. I guess there must be cheap way to do this, right?
Thanks
A query like this will show all recors, newest first:
SELECT *
FROM MyTable
ORDER BY Date DESC -- or some autoincrementing ID column
With an OFFSET clause, you can skip the first records.
This means that you get all records except the first 100 ones, i.e., you get those records that should be deleted:
SELECT *
FROM MyTable
ORDER BY Date DESC
LIMIT -1 OFFSET 100
You can then use this in a subquery to actually delete the records:
DELETE FROM MyTable
WHERE ID IN (SELECT ID
FROM MyTable
ORDER BY Date DESC
LIMIT -1 OFFSET 100)
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I have a database table with these columns:
Banner_Title varchar(500)
Existing_Banner_Image varchar(500)
Banner_URL varchar(500)
Banner_ALT varchar(500)
CheckBoxText varchar(500)
[for these 3 checkboxes have taken chkArticles,chkFittness,chkHealthArticle
but I want to check checkboxes also while insertion of data.For that I added one extra column in datatable named as sectionId for chkArticle checkbox I will assign 10 as a sectionId ,for chkFittness sectionId 11 and for chkHealthArticle as 12 so when I insert banner_title='article1', click chkArticle checkbox and fill other field data as mentioned in table format from then data should insert but next time when I try banner_title='article1' and click same checkbox then data not allowed to insert.but when I give banner_name='article1' and click another checkbox chkFittness it should allowed though the name of banner is same but maintained sectionid for checkboxes is different then what changes need to do stored procedure?? Basically I want to maintained unique banner_title for each checkbox click and to differentiate I maintained sectionid.plz help me
Create Unique constraint:
USE YourDatebase;
GO
ALTER TABLE YourTable
ADD CONSTRAINT YourConstraintName UNIQUE (Banner_Title);
GO
Check if banner title exists before insert attempt:
IF NOT EXISTS(SELECT Banner_Title FROM YourTable WHERE Banner_Title =
'TitleYourAreAttemptingToInsert')
BEGIN
INSERT .....
END
I have a database with a question table each question has a level attribute, topic, and the answers. I want to pick up randomly question in an ASP.net project but i don't want the same question to be repeated in the Details View.
This is the select statement:
SELECT TOP 3 [Question Number] AS Question_Number
,[Question Title] AS Question_Title
,[Answer 1] AS Answer_1
,[Answer 2] AS Answer_2
,[Answer 3] AS Answer_3
,QuizID
,Level
FROM Question
WHERE ( Level = 1 )
ORDER BY NEWID()
I don't think so you will get duplicate row until unless you have duplicate record in table. if you have then use DISTINCT to get unique record from table.
The basic syntax of DISTINCT keyword to eliminate duplicate records is as follows:
SELECT DISTINCT column1, column2,...columnN FROM table_name WHERE [condition]
http://www.w3schools.com/sql/sql_distinct.asp
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I want to update details using linq to entities. But instead of takin a new aspx page i want to update details in another view. will it work.? and please give the linq to entity update query
Let us assume:
db is the context of your Database Entity.
Table_name is the name of Table you need to update.
row_id is the value you are using to search for the data in the Table.
To update using linq you need to fetch the record first using the below query:
var data = (from r in db.Table_name
where r.id == row_id
select r).FirstOrDefault();
Now to update the values just update them. For example:
data.Name = "Firstname lastname"
data.IsActive = true;
.
.
and so on
After you have updated the values in data you need to Save the changes made by you by this command:
db.SaveChanges();
That's it.