Develop Reference

How do I update a value in a table based on some date interval?

So I have a Product table with a price.
I just want to update that price in a date interval.
Example:
apple is 10
And from 2018-02-02 to 2018-03-02 I want to update the price to 12.
I mention that I create a second table PriceInterval to insert the date interval.
enter code herePseudocode for my sqlscript

Hopefully I have understood the question correctly. A possible solution to what you're describing will mean changing the schema slightly. Having a new field in the product intervals for a new price between two dates allows you still keep the default price, when the interval is over. And using a query to select the price based on the date.
DROP TABLE IF EXISTS product_intervals;
DROP TABLE IF EXISTS products;
CREATE TABLE products (
ID INT NOT NULL AUTO_INCREMENT,
`Name` VARCHAR(50) NOT NULL,
Price DECIMAL(18,1) NOT NULL,
CONSTRAINT pkProductId PRIMARY KEY (ID)
);
CREATE TABLE product_intervals (
ID INT NOT NULL AUTO_INCREMENT,
ProductId INT NOT NULL,
DateTo DATETIME NOT NULL,
DateFrom DATETIME NOT NULL,
NewPrice DECIMAL(18,1) NOT NULL,
CONSTRAINT pkProductIntervalId PRIMARY KEY (ID),
CONSTRAINT fkProductId FOREIGN KEY (ProductId) REFERENCES `products`(`ID`) ON DELETE CASCADE
);
INSERT INTO products (`Name`, Price)
SELECT 'Apple', 0.10
UNION ALL SELECT 'Banana', 0.20;
INSERT INTO product_intervals (ProductId, DateTo, DateFrom, NewPrice)
SELECT 2, STR_TO_DATE('2018-02-10T00:00:00','%Y-%m-%dT%H:%i:%s'), STR_TO_DATE('2018-02-15T00:00:00','%Y-%m-%dT%H:%i:%s'), 0.30;
select p.`Name`, CASE WHEN pi.NewPrice IS NOT NULL THEN pi.NewPrice ELSE p.Price END AS Price
FROM products p
left join product_intervals pi ON p.ID = pi.ProductId AND DateFrom > NOW() AND DateTo < NOW();
The key part to this is the left join and the CASE statement in the select query. This code hasnt been fully tested, so it might need a bit of tweaking but hopefully will give you a good indication of what a solution could be.

How to find last inserted row in SQL server without identity column

I have created table like below:
create table EmployeeDetails
(
id int,
name varchar(50),
designation varchar(50),
ReportingTo int
)
And inserted rows like this:
insert into EmployeeDetails values(1, 'A', 'Developer', 3)
insert into EmployeeDetails values(5, 'E', 'CEO', 5)
insert into EmployeeDetails values(2, 'B', 'Developer', 3)
insert into EmployeeDetails values(3, 'C', 'Manager', 4)
insert into EmployeeDetails values(4, 'D', 'S.Manager', 5)
My question is: how can I identify the last inserted row in the table?
Used queries:
select IDENT_CURRENT('EmployeeDetails')
Select SCOPE_IDENTITY()
But I still didn't find the answer.
Replies are always welcome

You have a fundamental misunderstanding of tables in relational databases. They represent unordered sets. So, there is no "last row" in a table. The information on the ordering of rows has to be included when you create the table and/or load data into it.
In SQL Server, the simplest method is an identity column. That is why many tables are defined as:
create table EmployeeDetails (
id int identity primary key,
name varchar(50),
designation varchar(50),
ReportingTo int
);
You can also add default insertion time columns:
create table EmployeeDetails (
id int identity primary key,
name varchar(50),
designation varchar(50),
ReportingTo int,
CreatedAt datetime default gettime()
);
However, you can have multiple rows with the same datetime value.

You also can use rowversion like below,if you add a column
CREATE TABLE MyTest (myKey int
,myValue int, RV rowversion);
GO
INSERT INTO MyTest (myKey, myValue) VALUES (1, 0);
GO
INSERT INTO MyTest (myKey, myValue) VALUES (2, 0);
select * from mytest order by rv desc
Note:
This always give the last row inserted/Updated
References:
rowversion

Add fields of type datetime with name CreateDate and UpdateDate in your table, when you insert record in your table set their value for getdate()
After that you can run queries:
Select top 10 * from YourTable Order By CreateDate DESC
Or for last updated
Select top 10 * from YourTable Order By UpdateDate DESC

Please find my answer as below. Hope this may help you.
Add one more column to store record creation date/time as below.
create table EmployeeDetails
(
id int,
name varchar(50),
designation varchar(50),
ReportingTo int,
CreatedOn datetime
)
After table creation and inserting records write/execute query (here inner query is used) as below
select
*
from EmployeeDetails
where CreatedOn = (select max(CreatedOn) from EmployeeDetails )

Calling procedure from multi user

I have come up with scenario and i am really struggling with it. Please help me in this. i have table below and store procedure is calling for this table on button click in c# and data source is assign to grid.
Id Product QtyReceive QtyDispatch Location
1 HP2030 20 0 A
Below is procedure which is call on click event and it just select the require quantity of product which we require from specific location.
DECLARE #Data TABLE
(
Id int identity(1,1)
, Product varchar(10)
, QtyReceive int
, QTYDispatch int
, Location varchar(10)
)
DECLARE #Qty int = 10
INSERT #Data VALUES
('HP2030', 20 ,5,'A');
WITH sumqty AS
(
SELECT *, SUM(QtyReceive -QTYDispatch) OVER (PARTITION BY Product ORDER BY Id) AS TotalQty FROM #Data
)
,takeqty AS (
SELECT *,
CASE
WHEN #Qty >= TotalQty THEN QtyReceive
ELSE #Qty - ISNULL(LAG(TotalQty) OVER (PARTITION BY Product ORDER BY Id), 0)
END AS TakeQty
FROM sumqty
)
SELECT
Product
, TotalQty
, TakeQty
, Location
FROM takeqty WHERE TakeQty > 0
ORDER BY Location;
Now there is a problem let say two user sitting at two different computer and User 1 required 10 quantity and other user required 5 quantity. They click button to get quantity at same time and save it at same time and dispatch quantity update with quantity 10 instead of 10+5=15. It happens when both user hit save at same time. No of user can be vary. Is there any solution to this problem?
I try to understand the whole scenario.

InvalidOperationException on EF

I'm using WPF MVVM Pettern and
I Have a simple table on SQL Server 2012 which its ID(key) column is computed in an StoredProcedure, called PersonInsert: (This is simplified, but what is computed is more complex than this, anyway it's an int at last)
USE [Guard]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE [dbo].[PersonInsert]
#FName NVARCHAR(50) ,
#LName NVARCHAR(50) ,
#ID INT = NULL OUTPUT
AS
BEGIN
BEGIN TRY
SELECT #ID = ISNULL(MAX(ID), 0) + 1
FROM dbo.Person
INSERT INTO [dbo].[Person]
( [ID] ,
[FName] ,
[LName]
)
VALUES ( #ID ,
#FName ,
#LName
)
END TRY
BEGIN CATCH
DECLARE #ErrMsg NVARCHAR(MAX) ,
#ErrSvr INT ,
#ErrStt INT
SELECT #ErrMsg = ERROR_MESSAGE() + '|' + ERROR_PROCEDURE() + '|'
+ CAST(ERROR_LINE() AS NVARCHAR(5)) ,
#ErrSvr = ERROR_SEVERITY() ,
#ErrStt = ERROR_STATE()
RAISERROR (#ErrMsg, #ErrSvr, #ErrStt)
END CATCH
END
GO
In the .net side, I use EF 6.1 Code-First to handle data and mapped to SPs so I have OnModelCreating like this:
modelBuilder.Entity(Of Person)().MapToStoredProcedures(
Sub(x)
x.Insert(Function(e) e.HasName("[dbo].[PersonInsert]"))
x.Update(Function(e) e.HasName("[dbo].[PersonUpdate]"))
x.Delete(Function(e) e.HasName("[dbo].[PersonDelete]"))
End Sub)
And My Model is:
<Table("Person")> _
Partial Public Class Person
<DatabaseGenerated(DatabaseGeneratedOption.None), Key> _
Public Property ID As Integer
Public Property FName As String
Public Property LName as String
End Class
Now the strange thing is, when I try to Insert Data (Adding New Person) at first time, the db.SaveChanged() works great, but for second time it throws InvalidOperation exception with a message:
The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: Saving or accepting changes failed because more than one entity of type 'Shoniz.Guard.WPFGuardApplication.Person' have the same primary key value. Ensure that explicitly set primary key values are unique. Ensure that database-generated primary keys are configured correctly in the database and in the Entity Framework model. Use the Entity Designer for Database First/Model First configuration. Use the 'HasDatabaseGeneratedOption" fluent API or 'DatabaseGeneratedAttribute' for Code First configuration.
He is right! the data is comitted successfully! and I'm right too, because my ID(key) column is computed right and it's completely unique. Either I have used the DatabaseGeneratedAttribute with none value on ID, but the result is the same :(
Even when I re-query the db to check about duplicate keys, I find NOTHING!
Why this exception is thrown?
How can I prevent that?
Is there anyway to Ignore the changes after db.SaveChanges()?

First of all change DatabaseGeneratedOption.None to DatabaseGeneratedOption.Indetity
and finally change stored procedure to this:
BEGIN TRY
SELECT #ID = ISNULL(MAX(ID), 0) + 1
FROM dbo.Person
INSERT INTO [dbo].[Person]
( [ID] ,
[FName] ,
[LName]
)
VALUES ( #ID ,
#FName ,
#LName
)
--You have to tell EF this is returned Id of inserted person
SELECT #ID as ID
END TRY

Mysql normalization? Or another way?

After reading up on some normalization, it seems I am not quite grasping the concept.
What I am attempting to do is create a table that holds information for an item raffle.
So information for the item is ItemName, and Defindex.
After that, I need to have the "tickets" for the raffle, and to which user they went to. I want to limit the number of tickets sold.
So TicketA, TicketB, TicketC, TicketD.
Is there a query that I can use to insert a player name into TicketA if it's not full, or TicketB if A is full, so on until all tickets are sold?

Here's a sample to get you started: SQL Fiddle
Setup the basic tables to keep track of raffles and tickets.
CREATE TABLE Raffle
(
Id BIGINT AUTO_INCREMENT NOT NULL PRIMARY KEY
,Name VARCHAR(50) NOT NULL
,WinnerLimit INT NOT NULL
);
CREATE TABLE RaffleTicket
(
Id BIGINT AUTO_INCREMENT NOT NULL PRIMARY KEY
,RaffleId BIGINT NOT NULL
,UserId BIGINT NOT NULL
);
Setup a view to determine whether a raffle has any tickets left.
CREATE VIEW RaffleStatus
AS
SELECT Id AS RaffleId,
CASE WHEN EXISTS
(
SELECT 1
FROM RaffleTicket rt
WHERE rt.RaffleId = r.Id
GROUP BY rt.RaffleId
HAVING COUNT(rt.RaffleId) = r.WinnerLimit
)
THEN 1
ELSE 0
END AS SoldOut
FROM Raffle r;
Create a procedure to prevent overselling tickets. Note this probably isn't safe for multithreaded use.
DELIMITER //
CREATE PROCEDURE InsertRaffleTicket (IN userId BIGINT, IN raffleId BIGINT)
BEGIN
INSERT INTO RaffleTicket(UserId, RaffleId)
SELECT userId, raffleId
FROM RaffleStatus rs
WHERE rs.RaffleId = raffleId
AND rs.SoldOut = 0;
END//
DELIMITER ;

I want to limit the number of tickets sold.
That is business logic, not something that should reside in your database.
What if you want to query all raffles user X has attended? select * from raffles where ticketA = 'UserX' or ticketB = 'UserX' or ticketC = 'UserX'...
Just normalize it and check the ticket count from code.

One table of people, one of tickets, one of raffles.
Each ticket has the ID of the person and of the raffle.
As the previous answer, beyond that is business logic that shouldn't be in the DB. At most, you should "release" a batch of tickets for a raffle by creating them in the tickets table and then when a person wants to buy one you take the first ticket with the correct raffle ID and a null person ID.