I am trying to create a stored procedure to update 2 columns from a table in SQL Server. I have 2 tables products and order details.
Every time a product is sold, I want to update the product_quantity column, which means product_quantity - quantity (product on hand minus the quantity that is ordered). The product_quantity attribute should not go below 0.
I tried to build a view
drop view if exists v_products
go
create view v_products
as
select
product_name, product_quantity, product_status,
quantity, p.product_id
from
products p
inner join
order_details od on p.product_id = od.product_id
and then tried to create a procedure based on the view.
DROP PROCEDURE IF EXISTS p_products_product_quantity
GO
CREATE PROCEDURE p_products_product_quantity
#product_quantity INT,
#sold_quantity INT,
#product_status VARCHAR(50),
#product_id INT
AS
BEGIN
SET NOCOUNT ON;
UPDATE v_products
SET product_status = #product_status,
quantity = #sold_quantity,
product_quantity = #product_quantity,
product_id = #product_id
-- ,product_quantity = #product_quantity - #sold_quantity
WHERE #product_quantity - #sold_quantity = 0
END
I am expecting for example if I have
product_quantity 23
and quantity of the next order (sold quantity) is 23.
I want the product_quantity to change to 0 and product_status to 'not available'.
I see someone already mentioned that you can use a trigger for this so im going to give another alternative if you dont want to go down that route. You can just update both tables within the scope of your insert into the order table eg :
--Inserts order here
BEGIN TRY
BEGIN TRANSACTION
INSERT INTO order_detail
VALUES (#unit_price, #size, #quantity, #discount, GETDATE(),
#productid,
#orderid, #paymentid) --Im assuming you have already inserted into your order table in a different caller or same stored procedure
UPDATE product
SET product_quantity = (product_quantity - #quantity)
COMMIT;
END TRY
BEGIN CATCH
ROLLBACK;
END CATCH
In your stored procedure you will wrap it around a transaction so if all inserts and updates were successful it will commit that transaction to the database and if a single operation fails on the stored procedure then we rollback (all previous operations will be rolledback to ensure we dont create orphaned rows)
Hope this helps! :)
For a sync process, my SQL Server database should record a list items that have changed - table name and primary key.
The DB already has a table and stored procedure to do this:
EXEC #ErrCode = dbo.SyncQueueItem "tableName", 1234;
I'd like to add triggers to a table to call this stored procedure on INSERT, UPDATE, DELETE. How do I get the key? What's the simplest thing that could possibly work?
CREATE TABLE new_employees
(
id_num INT IDENTITY(1,1),
fname VARCHAR(20),
minit CHAR(1),
lname VARCHAR(30)
);
GO
IF OBJECT_ID ('dbo.sync_new_employees','TR') IS NOT NULL
DROP TRIGGER sync_new_employees;
GO
CREATE TRIGGER sync_new_employees
ON new_employees
AFTER INSERT, UPDATE, DELETE
AS
DECLARE #Key Int;
DECLARE #ErrCode Int;
-- How to get the key???
SELECT #Key = 12345;
EXEC #ErrCode = dbo.SyncQueueItem "new_employees", #key;
GO
The way to access the records changed by the operation is by using the Inserted and Deleted pseudo-tables that are provided to you by SQL Server.
Inserted contains any inserted records, or any updated records with their new values.
Deleted contains any deleted records, or any updated records with their old values.
More Info
When writing a trigger, to be safe, one should always code for the case when multiple records are acted upon. Unfortunately if you need to call a SP that means a loop - which isn't ideal.
The following code shows how this could be done for your example, and includes a method of detecting whether the operation is an Insert/Update/Delete.
declare #Key int, #ErrCode int, #Action varchar(6);
declare #Keys table (id int, [Action] varchar(6));
insert into #Keys (id, [Action])
select coalesce(I.id, D.id_num)
, case when I.id is not null and D.id is not null then 'Update' when I.id is not null then 'Insert' else 'Delete' end
from Inserted I
full join Deleted D on I.id_num = D.id_num;
while exists (select 1 from #Keys) begin
select top 1 #Key = id, #Action = [Action] from #Keys;
exec #ErrCode = dbo.SyncQueueItem 'new_employees', #key;
delete from #Keys where id = #Key;
end
Further: In addition to solving your specified problem its worth noting a couple of points regarding the bigger picture.
As #Damien_The_Unbeliever points out there are built in mechanisms to accomplish change tracking which will perform much better.
If you still wish to handle your own change tracking, it would perform better if you could arrange it such that you handle the entire recordset in one go as opposed to carrying out a row-by-row operation. There are 2 ways to accomplish this a) Move your change tracking code inside the trigger and don't use a SP. b) Use a "User Defined Table Type" to pass the record-set of changes to the SP.
You should use the Magic Table to get the data.
Usually, inserted and deleted tables are called Magic Tables in the context of a trigger. There are Inserted and Deleted magic tables in SQL Server. These tables are automatically created and managed by SQL Server internally to hold recently inserted, deleted and updated values during DML operations (Insert, Update and Delete) on a database table.
Inserted magic table
The Inserted table holds the recently inserted values, in other words, new data values. Hence recently added records are inserted into the Inserted table.
Deleted magic table
The Deleted table holds the recently deleted or updated values, in other words, old data values. Hence the old updated and deleted records are inserted into the Deleted table.
**You can use the inserted and deleted magic table to get the value of id_num **
SELECT top 1 #Key = id_num from inserted
Note: This code sample will only work for a single record for insert scenario. For Bulk insert/update scenarios you need to fetch records from inserted and deleted table stored in the temp table or variable and then loop through it to pass to your procedure or you can pass a table variable to your procedure and handle the multiple records there.
A DML trigger should operate set data else only one row will be processed. It can be something like this. And of course use magic tables inserted and deleted.
CREATE TRIGGER dbo.tr_employees
ON dbo.employees --the table from Northwind database
AFTER INSERT,DELETE,UPDATE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
declare #tbl table (id int identity(1,1),delId int,insId int)
--Use "magic tables" inserted and deleted
insert #tbl(delId, insId)
select d.EmployeeID, i.EmployeeID
from inserted i --empty when "delete"
full join deleted d --empty when "insert"
on i.EmployeeID=d.EmployeeID
declare #id int,#key int,#action char
select top 1 #id=id, #key=isnull(delId, insId),
#action=case
when delId is null then 'I'
when insId is null then 'D'
else 'U' end --just in case you need the operation executed
from #tbl
--do something for each row
while #id is not null --instead of cursor
begin
--do the main action
--exec dbo.sync 'employees', #key, #action
--remove processed row
delete #tbl where id=#id
--refill #variables
select top 1 #id=id, #key=isnull(delId, insId),
#action=case
when delId is null then 'I'
when insId is null then 'D'
else 'U' end --just in case you need the operation executed
from #tbl
end
END
Not the best solution, but just a direct answer on the question:
SELECT #Key = COALESCE(deleted.id_num,inserted.id_num);
Also not the best way (if not the worst) (do not try this at home), but at least it will help with multiple values:
DECLARE #Key INT;
DECLARE triggerCursor CURSOR LOCAL FAST_FORWARD READ_ONLY
FOR SELECT COALESCE(i.id_num,d.id_num) AS [id_num]
FROM inserted i
FULL JOIN deleted d ON d.id_num = i.id_num
WHERE (
COALESCE(i.fname,'')<>COALESCE(d.fname,'')
OR COALESCE(i.minit,'')<>COALESCE(d.minit,'')
OR COALESCE(i.lname,'')<>COALESCE(d.lname,'')
)
;
OPEN triggerCursor;
FETCH NEXT FROM triggerCursor INTO #Key;
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC #ErrCode = dbo.SyncQueueItem 'new_employees', #key;
FETCH NEXT FROM triggerCursor INTO #Key;
END
CLOSE triggerCursor;
DEALLOCATE triggerCursor;
Better way to use trigger based "value-change-tracker":
INSERT INTO [YourTableHistoryName] (id_num, fname, minit, lname, WhenHappened)
SELECT COALESCE(i.id_num,d.id_num) AS [id_num]
,i.fname,i.minit,i.lname,CURRENT_TIMESTAMP AS [WhenHeppened]
FROM inserted i
FULL JOIN deleted d ON d.id_num = i.id_num
WHERE ( COALESCE(i.fname,'')<>COALESCE(d.fname,'')
OR COALESCE(i.minit,'')<>COALESCE(d.minit,'')
OR COALESCE(i.lname,'')<>COALESCE(d.lname,'')
)
;
The best (in my opinion) way to track changes is to use Temporal tables (SQL Server 2016+)
inserted/deleted in triggers will generate as many rows as touched and calling a stored proc per key would require a cursor or similar approach per row.
You should check timestamp/rowversion in SQL Server. You could add that to the all tables in question (not null, auto increment, unique within database for each table/row etc).
You could add a unique index on that column to all tables you added the column.
##DBTS is the current timestamp, you can store today's ##DBTS and tomorrow you will scan all tables from that to current ##DBTS. timestamp/rowversion will be incremented for all updates and inserts but for deletes it won't track, for deletes you can have a delete only trigger and insert keys into a different table.
Change data capture or change tracking could do this easier, but if there is heavy volumes on the server or large number of data loads, partition switches scanning the transaction log becomes a bottleneck and in some cases you will have to remove change data capture to save the transaction log from growing indefinetely.
I am coming from Oracle background where I have used cursors for row updates.
Needed the easiest way to write looping logic. Here is the scenario
I have table1_intermediate which has Id,eligVal along with others
and table2_intermediatehas Id,inEligVal along with others
I have a main table table_main which has 3 columns Id,eligVal,inEligVal along with others
I want to insert records from both table1_intermediate and table2_intermediate into main table.
But if Id is already present( due to insert from one table), I want to update the same record coming from the 2nd intermediate table.
Any suggestions appreciated.
I prefer using two stored procedures. One to insert the value from table1 like ?:
Begin
If Not Exists (Select * from table_main where Id=#Id)
Begin
Insert into table_main(Id,eligVal) values(#Id,#eligVal)
End
End
and then insert a new row if Id is new or else update the same like :
Begin
If Not Exists (Select * from table_main where Id=#Id)
Begin
Insert into table_main(Id,inEligVal) values(#Id,#inEligVal)
End
Else
Begin
Update table_main Set inEligVal=#inEligVal where Id=#Id
End
End
I am trying to create a trigger which is triggered when an insert, delete happens in a table 'Abschaetzung_has_Varianten' and updates a table called 'Flag'. I need to select an ID from the same table to update the Flag table. Is the syntax wrong in writing the SELECT of the ID? I don't seem to get the #abschID from the select. Could anyone help me in this. Thank you.
CREATE TRIGGER trig_update_flag on [Abschaetzung_has_Varianten]
after insert, delete
As
Begin
DECLARE #x INT;
DECLARE #abschID INT;
DECLARE #value INT;
SELECT #value = 1;
SELECT #abschID = (SELECT TOP 1 Abschaetzung_ID FROM Abschaetzung_has_Varianten ORDER BY Abschaetzung_ID DESC);
SELECT #x = Count(*) FROM Flag WHERE AbschaetzID = #abschID
If #x > 0
Begin
UPDATE Flag Set [Flag] = #value WHERE AbschaetzID = #abschID;
end
end
Your code should be more like this:
CREATE TRIGGER trig_update_flag on [Abschaetzung_has_Varianten]
after insert, delete
as
begin
UPDATE Flag Set [Flag] = 1
WHERE AbschaetzID IN (SELECT DISTINCT Abschaetzung_ID FROM INSERTED)
UPDATE Flag Set [Flag] = 1
WHERE AbschaetzID IN (SELECT DISTINCT Abschaetzung_ID FROM DELETED)
end
INSERTED is a special trigger pseudo table that contains all of the updated or inserted records.
DELETED is a special trigger pseudo table that contains all of the deleted records.
This table may contain many records for one invocation of the trigger.
The code above is not the most efficient and may not suit your exact requirements but hopefully you get the idea.
I have the following trigger to avoid updating a certain column.
ALTER TRIGGER [dbo].[MyTrigger]
ON [dbo].[MyTable]
AFTER UPDATE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
IF UPDATE(SomeID)
BEGIN
DECLARE #id INT,
#newSomeID INT,
#currentSomeID INT
SELECT #id = ID, #newSomeID = SomeID
FROM inserted
SELECT #currentSomeID = SomeID
FROM deleted
WHERE ID = #id
IF (#newSomeID <> #currentSomeID)
BEGIN
RAISERROR ('cannot change SomeID (source = [MyTrigger])', 16, 1)
ROLLBACK TRAN
END
RETURN
END
END
Since i'm selecting from inserted and deleted, will this work if someone updates the table using a where clause that encapsulates multiple rows? In other words is it possible for the inserted and deleted table to contain more than one row within the scope of my trigger?
Thanks...
why not use an instead of update trigger and just join to INSERTED and push in all the columns except the one you don't want to update? your approach does not take in account that multiple rows can be affected by an single UPDATE statement.
try something like this:
ALTER TRIGGER [dbo].[MyTrigger]
ON [dbo].[MyTable]
INSTEAD OF UPDATE
AS
BEGIN
UPDATE m
SET col1=INSERTED.col1
,col2=INSERTED.col2
,col4=INSERTED.col4
FROM [dbo].[MyTable] m
INNER JOIN INSERTED i ON m.PK=i.PK
END
you could also try something like this:
ALTER TRIGGER [dbo].[MyTrigger]
ON [dbo].[MyTable]
AFTER UPDATE
AS
BEGIN
IF EXISTS(SELECT 1 FROM INSERTED i INNER JOIN DELETED d ON i.PK=d.PK WHERE i.SomeID!=d.SomeID OR (i.SomeID IS NULL AND d.SomeID IS NOT NULL) OR (d.SomeID IS NULL AND i.SomeID IS NOT NULL))
BEGIN
RAISERROR ('cannot change SomeID (source = [MyTrigger])', 16, 1)
ROLLBACK TRAN
RETURN
END
END
This will work for multiple row updates. Also, if the "SomeID" is NOT NULL you can remove the two OR conditions in the IF EXISTS
You need to define a cursor in trigger and get all affected records in cursor and then process it.