Trouble updating log with triggers using SQL Server - sql

Question

I am trying to create a trigger with a higher difficulty that would let me create a log after updating rows in alumns table
| Alumn_ID | Name | Courses | Favourite_Course
1 Peter 5 Math
And this would be the result if for example someone updated the number of courses from 5 to 6.
| Log_ID | Alumn_ID | Note | NoteID | Change_Date | Last_Change_Date
1 1 Fields were Updated Note 1 2018-04-23 00:00:00.000 2018-03-23 00:00:00.000
Here is my current trigger
ALTER TRIGGER [LOG]
ON ALUMNS
AFTER UPDATE
AS
BEGIN
DECLARE #Note VARCHAR(50)
DECLARE #Alumn_ID varchar;
SELECT #Alumn_ID= INSERTED.Alumn_ID FROM INSERTED
SET #Note = 'Fields were updated'
INSERT INTO Alumn_Log (Log_ID, Alumn_ID, Note, NoteID, Change_Date)
SELECT Log_ID, i.Alumn_ID, #Note, NoteID, GETDATE(); FROM INSERTED i
END
My problem is:
How do i create the Log ID and the Note ID that i can't take from INSERTED i?
My second problem is, how do i insert the current date? when i try to execute the query it tells me that i can't use that variable in INSERTS.
My third problem, is how can i put the "Last change date"?
Fourth, is there a way to type an specific Note for example if only the name was changed it should say "Name was changed"?
Finally, The Note ID would be Varchar not identity and every note ID needs to be different
This is the current and only error that's preventing me from running the Query:
This is what i get Msg 273, level 16, state 1, procedure Log_Trigger, line 19 [Batch Start Line 0] me time stamp Use INSERT with a list of columns to exclude the timestamp column or insert DEFAULT in the timestamp column.

Answer 1

Here is how I would approach it.
How do i create the Log ID and the Note ID that i can't take from
INSERTED i?
The Log Id can be an AutoIdentity column. An INT column with IDENTITY INSERT.
The Note ID can be an Auto Incremented Computed column (shown in the code below). You would probably need to introduce a new column that serves as a prefix.
My second problem is, how do i insert the current date? when i try to
execute the query it tells me that i can't use that variable in
INSERTS.
GETDATE()?
My third problem, is how can i put the "Last change date"?
You can have a join with INSERTED and get the value from the log from a previous row. Shown in the code.
Fourth, is there a way to type an specific Note for example if only
the name was changed it should say "Name was changed"?
That would depend on finding the nature of the update on which column. This is more of a business question than a technical question.
Finally, The Note ID would be Varchar not identity and every note ID needs to be different
Now, the code (the entire schema)
CREATE TABLE LOG(
Log_ID INT IDENTITY(1, 1) NOT NULL,
Alumn_ID INT,
NOTE VARCHAR(200),
PREFIX VARCHAR(30),
NOTEID AS([PREFIX] + RIGHT('0000000' + CAST(Log_ID AS VARCHAR(7)), 7)) PERSISTED,
CHANGEDATE DATETIME,
LASTCHANGEDATE DATETIME
);
CREATE TABLE ALUMN(
Alumn_ID INT,
NAME VARCHAR(50),
COURSES INT,
FAVORITE_COURSE VARCHAR(50)
);
CREATE TRIGGER[trg_LOG]
ON ALUMN
AFTER UPDATE
AS
BEGIN
DECLARE #Note VARCHAR(50)
--DECLARE #Alumn_ID VARCHAR(50)
DECLARE #Lastchange DATETIME
--SELECT #Alumn_ID = INSERTED.Alumn_ID FROM INSERTED
SET #Note = 'Fields were updated'
SELECT #Lastchange = CHANGEDATE FROM LOG l
INNER JOIN INSERTED i ON l.Alumn_ID = i.Alumn_ID
--INNER JOIN ALUMN
INSERT INTO LOG(Alumn_ID, Note, Prefix, CHANGEDATE, LASTCHANGEDATE)
SELECT i.Alumn_ID, #Note, 'AUP', GETDATE(), #Lastchange FROM INSERTED i
END

Answer 2

how do i insert the current date? when i try to execute the query it
tells me that i can't use that variable in INSERTS.
SELECT Log_ID, i.Alumn_ID, #Note, NoteID, GETDATE(); FROM INSERTED i
Take the semi-colon out of the line above.
SELECT Log_ID, i.Alumn_ID, #Note, NoteID, GETDATE() FROM INSERTED i