I have a table with no time stamp in any of the columns.
With what I have now in the table and without inserting any rows or redoing everything, is there a way to see what time and / or date a record was inserted?
Well, you can create a trigger in this table which when you insert, it will insert another record in another (or update another to count the times that it is inserted) table with the date and all the information that you want.
Creating a trigger which controls the inserted records is explained in another question in stackoverflow, I leave you the link here:
Trigger: How does the inserted table work? How to access its rows?
Related
I want to make a table which records update history for every single day.
I was trying to write sql, but got no idea how to make this table especially with update date.
How can I record update from all tables when it's been updated?
Suppose I have a table called invoices which has a column status. For invoice with ID of 10, I need to know when its status has been last updated.
I think you have to write 'before update' trigger and compare both values, existing in table and to be inserted. If the values differ, make an insert in log table(if you have it) and then update the master table with new values.
I made a trigger that is supposed to update another value in the same table a after I make an insert to the table. I do get the result I am looking for, but when I ask my teacher if it is correct he responded that this trigger updates "all" tables(?) and thus incorrect. He would not explain more than that (he is that kind of teacher...). Can anyone understand what he means? Not looking for the right code, just an explanation of what I might have misunderstood.
CREATE TRIGGER setDate
ON Loans
AFTER INSERT
AS
BEGIN
UPDATE Loans
set date = GETDATE()
END;
Your teacher intends to say that the query updates all rows in the table -- perhaps you misunderstood her or him.
The best way to do what you want is to use a default value:
alter table loans alter column date datetime default getdate();
That is, a trigger is not needed. If you did use a trigger, I'll give you two hints:
An instead of trigger.
inserted should be somewhere in the trigger.
Hello there. I upvoted your question because that might be the question of many beginners in SQL Server.
As I see you defined the trigger right! It is a correct way although it's not the best.
By the way we are not discussing all ways you could choose or not, I'm gonna correct your code and explain what your teacher meant.
Look at this UPDATE you wrote:
UPDATE Loans
SET date = GETDATE()
If you write a SELECT without a WHERE clause, what does it do? It would result all the rows in the table which was selected. right?
SELECT * FROM dbo.loans
So without a WHERE clause, your UPDATE will update all of the rows in the table.
OK now what to do to just update the only row ( or rows) which were recently inserted?
When you are writing a trigger, you are allowed to use this table: Inserted
which it has the rows were recently inserted. kinda these rows first come to this table and then go to the final destination table. So you can update them before they go the dbo.loans
it would be like this:
Update dbo.loans
SET date = GETDATE()
WHERE Id IN (SELECT * FROM Inserted)
In the following statement, will f1 always get the value that f2 used to have? Or will f2 sometimes get updated first and f1 winds up with NULL? I am under the impression that the new values are not available within the statement, that f2 has the old value while processing the record, but I can't find an authoritative place that says this.
UPDATE x
SET
x.f1 = x.f2,
x.f2 = NULL
Conceptually the operation happens "all at once" so it will use the "before" values
Indeed
UPDATE x
SET
x.f1 = x.f2,
x.f2 = x.f1
would also work fine to swap the two column values.
f1 will always get f2's previous value before the UPDATE.
Technically speaking the record is deleted, and reinserted. So SQL will work out what the new record should be, then delete the current record, and insert the new record afterwards.
This article regarding SQL Triggers may help explain:
The deleted table stores copies of the affected rows during DELETE and UPDATE statements. During the execution of a DELETE or UPDATE statement, rows are deleted from the trigger table and transferred to the deleted table. The deleted table and the trigger table ordinarily have no rows in common.
The inserted table stores copies of the affected rows during INSERT
and UPDATE statements. During an insert or update transaction, new
rows are added to both the inserted table and the trigger table. The
rows in the inserted table are copies of the new rows in the trigger
table.
http://msdn.microsoft.com/en-us/library/ms191300.aspx
I have a trigger that inserts a record into a diff table but I need to get that record that was inserted inside the trigger, how do I do it? There is no identity field, only account_nbr that is generated by a separate trigger on the insert table.
I don't know if there is sql statements to retrieve a row that was just inserted.
DB is Sql Server 2008.
The OUTPUT clause will give you back the records you have just inserted: http://msdn.microsoft.com/en-us/library/ms177564.aspx
If you mean the rows inserted before the trigger invoked, they are in the inserted pseudo-table.