How can I make the trigger wait? - sql-server

Question

I have a problem that I can not solve, I have a point of sale that inserts 3 tables after selling something, the header table, detail and customers (in that order).
I have a stored procedure that inserts the last record in the bak table, in the "text" column it inserts a concatenated of the 3 tables (it is fundamental), at the same time I have a stuff method that gathers all the details in a single row with the corresponding header (only one row per header), when executing the procedure after inserting it works normally, but when doing it with a trigger, an error appears that a null value can not be inserted in the "text" column, this is because the trigger points to the table header and the other 2 tables to a do not fill, if I put it at the level of detail, the stuff method does not work(since it inserts one record per header), the idea is to point to the header table but wait until everything is completed, there is some way to do it? I can not touch anything from the point of sale, everything would be at the database level (SQL SERVER 2008), can something be done? Can the trigger be delayed so that it waits for the completion of the filling of the other 2 tables?
--INTERMEDIATE TABLE
CREATE TABLE [bak]
(
[id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY,
[date] [date] NOT NULL,
[serie] [varchar](2) NOT NULL,
[text] [varchar](6000) NOT NULL
);
--STORE PROCEDURE
CREATE PROCEDURE sp_bak
AS
BEGIN
;
WITH CTE
AS (SELECT
h.date InsertDate,
h.series DocumentSerie,
('349891894' + h.date + h.series + h.total +
h.type + CHAR(13) + CHAR(10)) HeaderData,
(d.quantity + d.price + d.description + c.name +
c.identification) DetailData
FROM header h
FULL JOIN detail d
ON a.cod = b.cod
FULL JOIN customers c
ON b.cod = c.cod)
INSERT dbo.bak (date, serie, text)
SELECT TOP 1
InsertDate,
DocumentSerie,
HeaderData + REPLACE(STUFF((SELECT
';' + DetailData
FROM CTE C
WHERE C.HeaderData = T.HeaderData
FOR xml PATH ('')), 1, 1, ''), ';', CHAR(13) + CHAR(10))
FROM CTE T
GROUP BY HeaderData,
DocumentSerie,
InsertDate
order by InsertDate DESC
END
--TRIGGER
CREATE TRIGGER dbo.tr_bak
ON dbo.header
AFTER INSERT
AS
BEGIN
EXEC sp_bak
END
GO
--ERROR
Msg 515, Level 16, State 2, Procedure sp_bak, Line 4
Cannot insert the value NULL into column 'text', table 'VIDEOJUEGOS.dbo.bak'; column does not allow nulls. INSERT fails.

Answer 1

What I understand is: you have data coming into three tables and only after three tables have got the data, you have to insert data into BAK table. You dont have control over the when data will be coming to three tables.
I would suggest you below approaches:
Have a batch stored procedure: which is scheduled on regular basis and does these kinds of batch insertion. You can have a date filter for only picking the values, which got inserted after the previous run
Disclaimer: This is a bad approach of using triggers. You need to defined three triggers in three tables. Always check for the existence of records in all the three tables and generate header. If header value is NOT NULL then insert into the BAK table. So, here BAK table insert can come through any of the three triggers.

Answer 2

In your stored procedure for sp_bak, you can have the first statement as:
WAITFOR DELAY '00:00:05'
The time can be any number of seconds, but enough till the other tables gets inserted with values. The above statements delays the execution of the statements following the WAITFOR by 5 seconds.
Be aware, this might not be a good way to handle this kind of issue, because if the delay time is too high, the trigger might take time to execute and cause a delay of operations.