Question

I have a table for Contacts that I’m storing for customers with columns:

• Addressline1
• Addressline2
• CityID
• EmpID (FK)
• ModifiedDate (Computed, DateTime)

I use ASP.NET 4.0 and in the form I have used ASP.NET wizard with 3 steps. I have few problems.

1. How do I insert EmpID into a table dbo.Contacts where EmpID is a FK.
2. How to store ModifiedDate ? What is the sqlparameter to add the Time value?

Answer 1

You have basically two choices to keep a ModifiedDate up to date:

1. define a DEFAULT constraint on that column to get the current date/time when you freshly insert a row, and create an AFTER UPDATE trigger to update the ModifiedDate after every update operation on that row

2. set the ModifiedDate in your client application before every save operation to the database

Update: if you want to create an AFTER UPDATE trigger, use code something like this:

CREATE TRIGGER trg_UpdateModifiedDate
ON dbo.YourTableHere
AFTER UPDATE
AS
     UPDATE dbo.YourTableHere
     SET ModifiedDate = GETDATE()
     WHERE AddressID IN (SELECT AddressID FROM Inserted)

Here, I’m assuming your table YourTableHere has some kind of a primary key – a column like an ID that uniquely and clearly identifies each single row. Based on that row, you can update the ModifiedDate of all those rows that have been updated by a given SQL statement. Inserted is a pseudo table that’s available inside a trigger code body, which contains all the rows that have been modified by the operation that caused this trigger to fire (all rows affected by your UPDATE statement on YourTableHere)

Read more about triggers here:

• An Introduction to Triggers
• MSDN documentation on CREATE TRIGGER
• SQL Trigger Example in SQL Server 2008

Update #2: if your ModifiedDate column is in fact computed on the SQL Server table level, you cannot update it directly. You’ll need to find out what it’s computed from, and then you need to modify that column (if you can).

To find out what it’s computed from, run this query on your SQL Server database:

SELECT 
    c.name, c.is_computed, c.definition
FROM 
    sys.computed_columns c
WHERE 
    object_id = OBJECT_ID('dbo.Contacts')
    AND c.Name = 'ModifiedDate'