Click here to Skip to main content
14,175,662 members
Click here to Skip to main content
Add your own
alternative version


19 bookmarked
Posted 17 Jan 2005

Delete mechanism.

, 17 Jan 2005
Rate this:
Please Sign up or sign in to vote.
Explains a mechanism of deleting a record when the selected record has related records in other tables.


It is quite an often situation that during deletion of a record from the database there is a need to perform some action with all related records: delete related records, reassign them to another record (change foreign key), or remove information about relation (null foreign key).

For example, consider you have an Employees table and a Defects table and one employee’s record from Employees table is going to be deleted. There is a dilemma what to do with all the Defects assigned to that employee: delete them, leave them unassigned to any employee or assign them to another employee? The problem becomes even more difficult if there are many multilevel relations.

The mechanism described below will allow you to deal with this issue, and the source provided will help you to retrieve these related records.

Proposed scheme-plan to deal with the issue

  1. User asked to delete a certain record.
  2. Retrieve all the related records (IDs and foreign keys) from the database into a DataSet. In the example mentioned above there will be a record from Employees table to be deleted and all the related records (IDs and foreign keys) from the Defects table as well.
  3. Evaluate retrieved DataSet if there are any related records. In the simplest scenario, the application may inform the user about related records and restrict deletion. Or it may ask to approve deletion of related records as well or to change the foreign key of these records.
  4. Save changes to the database.


User asked to delete certain records

It is preferable to lock up the record for editing, the way in which only one user may work with it.

Note: The locking record topic is not discussed in this article. As well as the other solutions which do not allow users to modify or add records during this operation.

Retrieve all the related records

Retrieve all the related records (IDs and primary keys) in order to decide and perform specific action on those records. For this purpose, there is a utility function. It returns related records from different tables related to given table - record. You can find it in the class of DBDeleteHelper, under the namespace MohawkIDEAS.Utils.

public DataSet GetRelatedTables(SqlConnection con, 
    string strTableName, string strFieldName ,int iID);
  • con - Active connection.
  • strTableName - The table name to which the record belongs.
  • strFieldName – Primary field name.
  • iID – Record ID for the which you want to retrieve related records.

Tables are arranged in such a way that first comes the least related table (leafs). Last goes the main table. These tables are arranged as shown below:

Therefore, if you want to delete an employee with ID 12, you call the function:

DataSet _ds=GetRelatedTables(con, "employees","ID",12);

Evaluate retrieved DataSet

After you retrieve the DataSet you can check if there are any related records. For example, you can check if there are any related defects.

If (_ds.Tables["Defects"].Rows.Count>0 )




If there are any related records, these are the following options:

  • User may be informed that the selected record could not be deleted as there are related records, and cancel deletion.
  • All related records could be marked to be deleted as well:
    foreach (System.Data.DataRow _row in _ds.Tables["Defects"].Rows)
  • Related records may be updated (assigned to another employee) by changing foreign key value:
    int _iID;
    _iID = ChooseNewResposibleEmploee();
    foreach (System.Data.DataRow _row in _ds.Tables["Defects"].Rows)
        _row["EmployeeID"]= _iID; //Another Employee id

Saving changes to the database

If deletion was not canceled, the updated DataSet should be sent for updates:



This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Tadas Budvytis
Team Leader
Canada Canada
No Biography provided

You may also be interested in...

Comments and Discussions

GeneralExactly what I was looking for Pin
Bit-Smacker12-Mar-09 13:32
memberBit-Smacker12-Mar-09 13:32 
Thanks! I'm trying to find a way to copy an entire relation tree from a single root record to a new root record, and you helped point me in the right direction.

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Permalink | Advertise | Privacy | Cookies | Terms of Use | Mobile
Web05 | 2.8.190525.1 | Last Updated 17 Jan 2005
Article Copyright 2005 by Tadas Budvytis
Everything else Copyright © CodeProject, 1999-2019
Layout: fixed | fluid