Creating a status update trigger - sql

Question

I have 2 tables like so:
JOBS table
Jobcode UserId Status
101 130 R
102 139 D
USERS table
UserId Email
130 test#example.com
I want to create a trigger on insert and update that sends an email to my stored procedure:
EXEC dbo.SendMyEmail #email, #jobcode;
when the jobcode is inserted as 'D' or updated to 'D'.

Answer 1

In my opinion, sending email in a trigger is not optimal.
Instead, you should just insert to a queue table, and have a process run frequently that checks the table and sends the email.
What happens if you get an error in your email procedure? It will force a rollback of your job completion status. Only you know whether that is minor or possibly catastrophic. But I can tell you for sure that DB best practice is to NOT do extended I/O during a DML operation.
CREATE TRIGGER TR_Jobs_EnqueueEmail_IU ON dbo.Jobs FOR INSERT, UPDATE
AS
SET NOCOUNT ON;
INSERT dbo.EmailQueue (UserID, JobCode)
SELECT UserID, JobCode
FROM
Inserted I
LEFT JOIN Deleted D
ON I.JobCode = D.JobCode -- or proper PK columns
WHERE
IsNull(D.Status, 'R') <> 'D'
AND I.Status = 'D';
Tables needed:
CREATE TABLE dbo.EmailQueue (
QueuedDate datetime NOT NULL
CONSTRAINT DF_EmailQueue_QeueueDate DEFAULT (GetDate()),
UserID int NOT NULL,
JobCode int NOT NULL,
CONSTRAINT PK_EmailQueue PRIMARY KEY CLUSTERED (QueuedDate, UserID, JobCode)
);
CREATE TABLE dbo.EmailSent (
SentDate datetime NOT NULL
CONSTRAINT DF_EmailSent_SentDate DEFAULT (GetDate()),
QueuedDate datetime NOT NULL,
UserID int NOT NULL,
JobCode int NOT NULL,
CONSTRAINT PK_EmailSent PRIMARY KEY CLUSTERED (SentDate, QueuedDate, UserID, JobCode)
);
Then, run the following stored procedure once a minute from a SQL Job:
CREATE PROCEDURE dbo.EmailProcess
AS
DECLARE #Email TABLE (
QueuedDate datetime,
UserID int,
JobCode int
);
DECLARE
#EmailAddress nvarchar(255),
#JobCode int;
WHILE 1 = 1 BEGIN
DELETE TOP 1 Q.*
OUTPUT Inserted.QueuedDate, Inserted.UserID, Inserted.JobCode
INTO #Email (QueuedDate, UserID, JobCode)
FROM dbo.EmailQueue Q WITH (UPDLOCK, ROWLOCK, READPAST)
ORDER BY QueuedDate;
IF ##RowCount = 0 RETURN;
SELECT #EmailAddress = U.EmailAddress, #JobCode = E.JobCode
FROM
#Email E
INNER JOIN dbo.User U
ON E.UserID = U.UserID;
EXEC dbo.SendMyEmail #EmailAddress, #JobCode;
DELETE E
OUTPUT QueuedDate, UserID, JobCode
INTO dbo.EmailSent (QueuedDate, UserID, JobCode)
FROM #Email E;
END;
The delete pattern and locks I used are very specifically chosen. If you change them or change the delete pattern in any way it is almost certain you will break it. Handling locks and concurrency is hard. Don't change it.
Note: I typed all the above without checking anything on a SQL Server. It is likely there are typos. Please forgive any.

Answer 2

I'm not sure about data types etc but this should at least put you on the right track.
Hope it helps...
CREATE TRIGGER SendEmailOnStatusD
ON JOBS
-- trigger is fired when an update is made for the table
FOR UPDATE --You can add the same for INSERT
AS
-- holds the UserID so we know which Customer was updated
DECLARE #UserID int
DECLARE #JobCode int
SELECT #UserID = UserId, #JobCode = JobCode
FROM INSERTED WHERE [Status] = 'D' --If you want the old value before the update, use 'deleted' table instead of 'inserted' table
IF (#UserID IS NOT NULL)
BEGIN
-- holds the email
DECLARE #email varchar(250)
SELECT #email = Email FROM USERS WHERE UserId = #UserID
EXEC SendMyEmail (#email, #jobcode);
END
GO
EDIT:
Above code does not handle multiple updates, so for better practice see below option
CREATE TRIGGER SendEmailOnStatusD ON JOBS
-- trigger is fired when an update is made for the table
FOR UPDATE --You can add the same for INSERT
AS
DECLARE #Updates table(UserID int, JobCode int, Email varchar(250))
INSERT INTO #Updates (UserID, JobCode, Email)
SELECT i.UserID, i.JobCode, u.Email
FROM INSERTED i
JOIN USERS u ON i.UserID = u.UserID
WHERE [Status] = 'D'
DECLARE #UserID int
DECLARE #JobCode int
DECLARE #Email varchar(250)
WHILE EXISTS(SELECT * FROM #Updates)
BEGIN
SELECT TOP 1
#UserID = UserID,
#Email = Email,
#JobCode = JobCode
FROM #Updates WHERE UserID = #UserID
EXEC SendMyEmail (#email, #jobcode);
DELETE FROM #Updates
WHERE UserID = #UserID
END
GO
Additionally, as discussed in the comments, sending emails from a trigger is also not the best, but as this is what the question asks for it has been included. I would recommend alternative options for sending emails such as a queue which has been mentioned in other answers.