how to add and delete but the records should be maintained

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hi,
I m working in a library project.
I have two forms i.e frmBooks and frmIssueRegister
and tables books and Issue
My fields in table books are : Totalcopies, IssuedCopies,LeftCopies
when I m issuing a book (frmIssueRegister)and on saving it should
do the following changes in frmBooks:
Total copies= 10
Issued copies=3
Left Copies in library = 7

similarly on returning i book ,it should subtract:
Total copies= 10
Issued copies=2
Left Copies in library = 8

Please help me out !!!

Posted 22-May-12 23:14pm

Member 8575950

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Maciej Los 23-May-12 11:50am

Not clear! What kind of database?

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Wendelius · Answer 1 · 2012-05-23T10:29:00

Solution 4

I would advice to store only the amount of total copies and issued copies. Copies left in library can be calculated at any time so when you fetch the data you can use something like:

SQL

SELECT TotalCopies,
       IssuedCopies,
       TotalCopies - IssuedCopies AS CopiesLeft
FROM ...

It's a good rule of thumb that calculated fields should never be store (at least in a way that they can be modified).

Posted 23-May-12 10:29am

Wendelius

v2

Comments

Espen Harlinn 23-May-12 18:24pm

Good points :-D

Wendelius 24-May-12 15:08pm

Thank you Espen :)

uspatel · Answer 2 · 2012-05-22T23:22:00

Solution 2

use update query like
when Issue

SQL

update frmIssueRegister set Issuedcopies=Issuedcopies+1,leftCopies=leftCopies-1 where bookid='123'

hope it will helps you

Posted 22-May-12 23:22pm

uspatel

Nilesh Patil Kolhapur · Answer 3 · 2012-05-23T02:26:00

Solution 3

Hi,
to maintain this u need to use before trigger
to write a trigger refer this[^]

Best luck

Posted 23-May-12 2:26am

Nilesh Patil Kolhapur

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Member 8575950 24-May-12 1:47am

I am new to vb.net. Can you pls help me in writting this trigger

Savalia Manoj M · Answer 4 · 2012-05-24T17:29:00

Solution 5

Hi,
If You use SQL Server 2005 or letter version theh you can assign Left Copies field to Calculated field.
There is facility to set calculated field.

Posted 24-May-12 17:29pm

Savalia Manoj M

ythisbug · Answer 5 · 2012-05-24T19:03:00

hi u can try this
assume ur having table name tblCopies
columns
cCopies(Money)
while adding from aspx page..u (add) + with numbers (means how many copies returned )
and while issuing -(minus) with numbers means how many issued

then now u just write simple query

Select SUM(cCopies) from tblCopies.

hope it will helps u

Member 8226665 · Answer 6 · 2012-05-22T23:17:00

Solution 1

use tracnstion for doing this

Posted 22-May-12 23:17pm

Member 8226665

how to add and delete but the records should be maintained

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