how to deduct a quantity from a database using VB.NET

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hello, i am new here.

I am planning to create a simple POS system but i don't know how to deduct a quantity from the database.

i have a database named "Database1.mdb"
and I have a table named "tblitem"
i have 2 field names "itemname" and "quantity"

On VB.Net, i have 1 textbox and 1 button.

Each time i press the button, i want to deduct a quantity from the database depends on the number i input on the extbox

for example i have in my database:

ItemName:apple
Quantity: 100

and if i input "1" on the textbox and press the button it will deduct 1 apple from the database

ItemName: apple
Quantity: 99

please help me. i don't know how to code it. please help me. sorry for my english

Posted 4-Mar-13 4:05am

rotsen28

Updated 11-Mar-18 0:52am

v2

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Maciej Los 4-Mar-13 10:21am

What have you done till now?

1 solution

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OriginalGriff · Accepted Answer · 2013-03-04T05:04:00

Solution 1

Try:

VB

Using con As New SqlConnection(strConnect)
	con.Open()
	Using com As New SqlCommand("UPDATE tblitem SET [quantity]=[quantity] - @QU WHERE itemname=@IN", con)
		com.Parameters.AddWithValue("@QU", myTextBox.Text)
		com.Parameters.AddWithValue("@IN", "apple")
		com.ExecuteNonQuery()
	End Using
End Using

Posted 4-Mar-13 5:04am

OriginalGriff

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rotsen28 4-Mar-13 22:24pm

Thanks for your solution. But i just want to ask what is @QU?

OriginalGriff 5-Mar-13 3:57am

@QU is a parameter name - it ties the position you want to use it in the SQL command with the Parameter value you set in the AddWithValue statement.