I recently created a SQL trigger to replace a very expensive query I used to run to reduce the amount of updates my database does each day.
Before I preform an update I check to see how many updates have already occurred for the day, this used to be done by querying:
SELECT COUNT(*) FROM Movies WHERE DateAdded = Date.Now
Well my database has over 1 million records and this query is run about 1-2k a minute so you can see why I wanted to take a new approach for this.
So I created an audit table and setup a SQL Trigger to update this table when any INSERT or UPDATE happens on the Movie table. However I'm noticing the audit table is getting out of sync by a few hundred everyday (the audit table count is higher than the actual updates in the movie table). As this does not pose a huge issue I'm just curious what could be causing this or how to go about debugging it?
SQL Trigger:
ALTER TRIGGER [dbo].[trg_Audit]
ON [dbo].[Movies]
AFTER UPDATE, INSERT
AS
BEGIN
UPDATE Audit SET [count] = [count] + 1 WHERE [date] = CONVERT (date, GETDATE())
IF ##ROWCOUNT=0
INSERT INTO audit ([date], [count]) VALUES (GETDATE(), 1)
END
The above trigger only happens after an UPDATE or INSERT on the Movie table and tries to update the count + 1 in the Audit table and if it doesn't exists (IF ##ROWCOUNT=0) it then creates it. Any help would be much appreciated! Thanks.
Something like this should work:
create table dbo.Movies (
A int not null,
B int not null,
DateAdded datetime not null
)
go
create view dbo.audit
with schemabinding
as
select CONVERT(date,DateAdded) as dt,COUNT_BIG(*) as cnt
from dbo.Movies
group by CONVERT(date,DateAdded)
go
create unique clustered index IX_MovieCounts on dbo.audit (dt)
This is called an indexed view. The advantage is that SQL Server takes responsibility for maintaining the data stored in this view, and it's always right.
Unless you're on Enterprise/Developer edition, you'd query the audit view using the NOEXPAND hint:
SELECT * from audit with (noexpand)
This has the advantages that
a) You don't have to write the triggers yourself now (SQL Server does actually have something quite similar to triggers behind the scenes),
b) It can now cope with multi-row inserts, updates and deletes, and
c) You don't have to write the logic to cope with an update that changes the DateAdded value.
Rather than incrementing the count by 1 you should probably be incrementing it by the number of records that have changed e.g.
UPDATE Audit
SET [count] = [count] + (SELECT COUNT(*) FROM INSERTED)
WHERE [date] = CONVERT (date, GETDATE())
IF ##ROWCOUNT=0
INSERT INTO audit ([date], [count])
VALUES (GETDATE(), (SELECT COUNT(*) FROM INSERTED))
Related
The trigger below select ID's from one table (employeeInOut), sums int's in a column in that table matching all ID's, and is supposed to insert these in another table (monthlyHours). I can't figure out if this is a syntax problem (nothing shows up in intellisense), and all it says is trigger executed successfully - nothing is inserted.
Trigger ->
GO
CREATE TRIGGER empTotalsHoursWorked
ON employeeInOut
FOR INSERT, DELETE, UPDATE
AS
BEGIN
INSERT INTO monthlyHours(employeeID, monthlyHours)
SELECT (SELECT employeeID FROM employeeInOut),
SUM(dailyHours) AS monthlyHours
FROM employeeInOut
WHERE employeeInOut.employeeID=(SELECT employeeID FROM monthlyHours)
END
GO
I have re-worked this trigger many times and this is the one with no errors, however nothing is inserted, and results seem to be nothing. Any advice, answers please appreciated.
Going with a couple of assumptions here one being that monthlyHours table contains employeeID and monthlyhours.
With that being said I think you are going to need multiple triggers depending on the action. Below is an example based on insert into the employeeInOut table
GO
CREATE TRIGGER empTotalsHoursWorked
ON employeeInOut
AFTER INSERT
AS
BEGIN
DECLARE #employeeID INT
DECLARE #monthlyHours INT
SELECT #employeeID = INSERTED.employeeID
FROM INSERTED
SELECT #monthlyHours = SUM(dailyHours)
FROM employeeInOut
WHERE employeeInOut.employeeID = #employeeID
INSERT INTO monthlyHours(employeeID,monthlyHours)
values (#employeeID, #monthlyHours)
END
GO
This will insert a new row of course. You may want to modify this to update the row if the row already exists in the monthlyHours table for that employee.
I would really advise against a trigger for a simple running total like this, your best option would be to create a view. Something like:
CREATE VIEW dbo.MonthlyHours
AS
SELECT EmployeeID,
monthlyHours = SUM(dailyHours)
FROM dbo.employeeInOut
GROUP BY EmployeeID;
GO
Then you can access it in the same way as your table:
SELECT *
FROM dbo.MonthlyHours;
If you are particularly worried about performance, then you can always index the view:
CREATE VIEW dbo.MonthlyHours
WITH SCHEMABINDING
AS
SELECT EmployeeID,
monthlyHours = SUM(dailyHours),
RecordCount = COUNT_BIG(*)
FROM dbo.employeeInOut
GROUP BY EmployeeID;
GO
CREATE UNIQUE CLUSTERED INDEX UQ_MonthlyHours__EmployeeID ON dbo.MonthlyHours(EmployeeID);
Now whenever you add or remove records from employeeInOut SQL Server will automatically update the clustered index for the view, you just need to use the WITH (NOEXPAND) query hint to ensure that you aren't running the query behind the view:
SELECT *
FROM dbo.MonthlyHours WITH (NOEXPAND);
Finally, based on the fact the table is called monthly hours, I am guessing it should be by month, as such I assume you also have a date field in employeeInOut, in which case your view might be more like:
CREATE VIEW dbo.MonthlyHours
WITH SCHEMABINDING
AS
SELECT EmployeeID,
FirstDayOfMonth = DATEADD(MONTH, DATEDIFF(MONTH, 0, [YourDateField]), 0),
monthlyHours = SUM(dailyHours),
RecordCount = COUNT_BIG(*)
FROM dbo.employeeInOut
GROUP BY EmployeeID, DATEADD(MONTH, DATEDIFF(MONTH, 0, [YourDateField]), 0);
GO
CREATE UNIQUE CLUSTERED INDEX UQ_MonthlyHours__EmployeeID_FirstDayOfMonth
ON dbo.MonthlyHours(EmployeeID, FirstDayOfMonth);
And you can use the view in the same way described above.
ADDENDUM
For what it is worth, for your trigger to work properly you need to consider all cases:
Inserting a record where that employee already exists in MonthlyHours (Update existing).
Inserting a record where that employee does not exist in MonthlyHours (insert new).
Updating a record (update existing)
Deleting a record (update existing, or delete)
To handle all of these cases you can use MERGE:
CREATE TRIGGER empTotalsHoursWorked
ON employeeInOut
FOR INSERT, DELETE, UPDATE
AS
BEGIN
WITH ChangesToMake AS
( SELECT EmployeeID, SUM(dailyHours) AS MonthlyHours
FROM ( SELECT EmployeeID, dailyHours
FROM Inserted
UNION ALL
SELECT EmployeeID, -dailyHours
FROM deleted
) AS t
GROUP BY EmployeeID
)
MERGE INTO monthlyHours AS m
USING ChangesToMake AS c
ON c.EmployeeID = m.EmployeeID
WHEN MATCHED THEN UPDATE
SET MonthlyHours = c.MonthlyHours
WHEN NOT MATCHED BY TARGET THEN
INSERT (EmployeeID, MonthlyHours)
VALUES (c.EmployeeID, c.MonthlyHours)
WHEN NOT MATCHED BY SOURCE THEN
DELETE;
END
GO
I'm working on a simple VB NET/WPF application that communicates with a SQL Server 2012 database, which at least two or more people could be using at the same time.
To keep track of any and every change in the database (INSERT/UPDATE/DELETE), I'm implementing a simple trigger-based auditing system, where obviously, any data getting updated/deleted/inserted is saved in its corresponding auditing table, while also keeping track of the user and the date/time of the operation.
I obviously found tons of guides while searching. But I noticed that most of these SQL Server guides would use JOINs in their queries to extract the data stored in the Inserted or Deleted tables, while I achieved the same result without any JOINs.
Exemple :
My INSERT trigger :
CREATE TRIGGER [HumanResources].[after_insert_humanresources_shift]
ON [HumanResources].[Shift]
AFTER INSERT
AS
BEGIN
INSERT INTO [HumanResources].[Shift_Audit]
(
-- [EventID], [EventBy] and [EventOn] have autovalues
[EventType],
[ShiftID],
[Name],
[StartTime],
[EndTime],
[ModifiedDate]
)
SELECT
'INSERT',
[ShiftID],
[Name],
[StartTime],
[EndTime],
[ModifiedDate]
FROM
[Inserted]
END
This guide's INSERT Trigger :
create trigger tblTriggerAuditRecord on tblOrders
after insert
as
begin
insert into tblOrdersAudit
(OrderID, OrderApprovalDateTime, OrderStatus, UpdatedBy, UpdatedOn )
select i.OrderID, i.OrderApprovalDateTime, i.OrderStatus, SUSER_SNAME(), getdate()
from tblOrders t
inner join inserted i on t.OrderID=i.OrderID
end
My DELETE and UPDATE triggers do exactly the same thing. And all these work for both single D/U/I queries or multiple ones (multiple Updates in a single query for instance). Is there a specific reason why I should be using JOINs ?
Yes the "inner join inserted i on t.OrderID=i.OrderID" checks for dependencies on orders table, and will insert only records where there are genuine orders in the orders table, inserting to independent tables does not test the data for dependencies at entity level. hope that helps.
We have a database with one table for all of our Employee information, (name, pay, etc). One of the columns in the table is "commission." I am trying to write a trigger that will only allow the "commission" column be updated or inserted into if it is for a Sales Representative. If an update is tried on any other employee then it should print out an error. I would like this trigger to also print all of the information from each update, failed or not, to a separate table. What is the best way for me to go about doing this?
I am relatively new to SQL Server so any help here would be greatly appreciated!
Thanks,
EDIT:
Here is what i have so far:
CREATE TRIGGER CommissionUpdate ON Employees
FOR UPDATE
AS IF UPDATE(Commission)
Declare
#Old_Comm money
, #New_Comm money
, #EmpID int
Select #EmpID = (Select EmployeeID From Deleted)
Select #Old_Comm = (Select Commission From Deleted)
Select #New_Comm = (Select Commission From Inserted)
BEGIN
INSERT INTO ChangeLog (EmpID, [User], [Date], OldComm, NewComm)
VALUES (#EmpID, User_Name(), GetDate(), #Old_Comm, #New_Comm)
END
Basically all this does is add entries to the ChangeLog table when the commission table is updated. Im still having trouble adding the constraints to only allow "commission" to be updated for Sales Reps.
I have a DB in SQL server and one of the tables recieves a large amount of data every day (+100 000). The data is reported on, but my client only needs it for 7 days. On the odd occasion he will require access to historic data, but this can be ignored.
I need to ensure that my primary lookup table stays as small as can be (so that my queries are as quick as possible), and any data older than 7 days goes into a secondary (archiving) table, within the same database. Data feeds in consistently to my primary table throughout the day from a variety of data sources.
How would I go about performing this? I managed to get to the code below through using other questions, butI am now recieving an error ("Msg 8101, Level 16, State 1, Line 12
An explicit value for the identity column in table 'dbo.Archived Data Import' can only be specified when a column list is used and IDENTITY_INSERT is ON. ").
Below is my current code:
DECLARE #NextIDs TABLE(IndexID int primary key)
DECLARE #7daysago datetime
SELECT #7daysago = DATEADD(d, -7, GetDate())
WHILE EXISTS(SELECT 1 FROM [dbo].[Data Import] WHERE [Data Import].[Receive Date] < #7daysago)
BEGIN
BEGIN TRAN
INSERT INTO #NextIDs(IndexID)
SELECT TOP 10000 IndexID FROM [dbo].[Data Import] WHERE [Data Import].[Receive Date] < #7daysago
INSERT INTO [dbo].[Archived Data Import]
SELECT *
FROM [dbo].[Data Import] AS a
INNER JOIN #NextIDs AS b ON a.IndexID = b.IndexID
DELETE [dbo].[Data Import]
FROM [dbo].[Data Import]
INNER JOIN #NextIDs AS b ON a.IndexID = b.IndexID
DELETE FROM #NextIDs
COMMIT TRAN
END
What am I doing wrong here? Im using SQL server 2012 Express, so cannot partition (which would be ideal).
Beyond this, how do I turn this into a daily recurring task? Any help would be much appreciated.
An explicit value for the identity column in table 'dbo.Archived Data Import' can only be specified when a column list is used and IDENTITY_INSERT is ON
So... set identity insert on. Also, use DELETE ... OUTPUT INTO ... rather than SELECT ->
INSERT -> DELETE.
DECLARE #7daysago datetime
SELECT #7daysago = DATEADD(d, -7, GetDate());
SET IDENTITY_INSERT [dbo].[Archived Data Import] ON;
WITH CTE as (
SELECT TOP 10000 *
FROM [dbo].[Data Import]
WHERE [Data Import].[Receive Date] < #7daysago)
DELETE CTE
OUTPUT DELETED.id, DELTED.col1, DELETED.col2, ...
INTO [dbo].[Archived Data Import] (id, col1, col2, ....);
Beyond this, how do I turn this into a daily recurring task?
Use conversation timers and activated procedures. See Scheduling Jobs in SQL Server Express.
Without seeing your Table definitions, I am going to assume that your archive table has the same definition as your current table. Am I right in assuming that You have an identity column as Archived Data Import.IndexID? If so, switch it to ba an int large enough to hold expected values.
In order to schedule, this you will need to create a bat file to run this procedure and schedule it with windows scheduler.
I've got a stored procedure, which selects 1 record back. the stored procedure could be called from several different applications on different PCs. The idea is that the stored procedure brings back the next record that needs to be processed, and if two applications call the stored proc at the same time, the same record should not be brought back. My query is below, I'm trying to write the query as efficiently as possible (sql 2008). Can it get done more efficiently than this?
CREATE PROCEDURE GetNextUnprocessedRecord
AS
BEGIN
SET NOCOUNT ON;
--ID of record we want to select back
DECLARE #iID BIGINT
-- Find the next processable record, and mark it as dispatched
-- Must be done in a transaction to ensure no other query can get
-- this record between the read and update
BEGIN TRAN
SELECT TOP 1
#iID = [ID]
FROM
--Don't read locked records, only lock the specific record
[MyRecords] WITH (READPAST, ROWLOCK)
WHERE
[Dispatched] is null
ORDER BY
[Received]
--Mark record as picked up for processing
UPDATE
[MyRecords]
SET
[Dispatched] = GETDATE()
WHERE
[ID] = #iID
COMMIT TRAN
--Select back the specific record
SELECT
[ID],
[Data]
FROM
[MyRecords] WITH (NOLOCK, READPAST)
WHERE
[ID] = #iID
END
Using the READPAST locking hint is correct and your SQL looks OK.
I'd add use XLOCK though which is also HOLDLOCK/SERIALIZABLE
...
[MyRecords] WITH (READPAST, ROWLOCK, XLOCK)
...
This means you get the ID, and exclusively lock that row while you carry on and update it.
Edit: add an index on Dispatched and Received columns to make it quicker. If [ID] (I assume it's the PK) is not clustered, INCLUDE [ID]. And filter the index too because it's SQL 2008
You could also use this construct which does it all in one go without XLOCK or HOLDLOCK
UPDATE
MyRecords
SET
--record the row ID
#id = [ID],
--flag doing stuff
[Dispatched] = GETDATE()
WHERE
[ID] = (SELECT TOP 1 [ID] FROM MyRecords WITH (ROWLOCK, READPAST) WHERE Dispatched IS NULL ORDER BY Received)
UPDATE, assign, set in one
You can assign each picker process a unique id, and add columns pickerproc and pickstate to your records. Then
UPDATE MyRecords
SET pickerproc = myproc,
pickstate = 'I' -- for 'I'n process
WHERE Id = (SELECT MAX(Id) FROM MyRecords WHERE pickstate = 'A') -- 'A'vailable
That gets you your record in one atomic step, and you can do the rest of your processing at your leisure. Then you can set pickstate to 'C'omplete', 'E'rror, or whatever when it's resolved.
I think Mitch is referring to another good technique where you create a message-queue table and insert the Ids there. There are several SO threads - search for 'message queue table'.
You can keep MyRecords on a "MEMORY" table for faster processing.