Please am new in vb.net and sql server, I have created a two tables in database called Service and Trans.
Create Table Service(
ServiceID int,
ServiceName varchar(30),
ServiceStartValue int
);
Create Table Trans(
EntryTS datetime,
EntryCounter int,
ServedTS datetime,
ServedCounter int,
Skipped int
);
I am trying to create a 'transaction and trigger' that will check and update ServedCounter based on the values in EntryCounter upon ServiceID which the update statement must not allow the ServedCounter > EntryCounter.
I don't quite understand the full requirement, but here's how you can prevent a update (or insert) from happening with a trigger.
CREATE TRIGGER Trans_upd_trg ON Trans AFTER INSERT, UPDATE
AS
BEGIN
SET NOCOUNT ON;
--Don't allow the update
IF EXISTS(SELECT 1 FROM inserted WHERE ServedCounter > EntryCounter)
RAISERROR ('ServedCounter > EntryCounter', 16, 1 );
END
GO
Within the context of the trigger you have two logical tables, INSERTED, and DELETED.
These tables contain the old and new values. (deleted is empty for a insert operation)
Hope that helps.
Use a Instead Of Trigger
CREATE TRIGGER Trans_upd_trg
ON Trans
Instead OF INSERT, UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF EXISTS (SELECT *
FROM inserted
WHERE ServedCounter > EntryCounter)
AND EXISTS (SELECT *
FROM deleted)
UPDATE A
SET EntryTS = I.EntryTS,
EntryCounter = I.EntryCounter,
ServedTS = I.ServedTS,
ServedCounter = I.ServedCounter,
Skipped = I.Skipped
FROM Trans A
JOIN inserted I
ON A.EntryTS = I.EntryTS
AND A.ServedTS = I.ServedTS
WHERE i.ServedCounter > i.EntryCounter
ELSE
INSERT INTO Trans
SELECT *
FROM inserted
WHERE ServedCounter > EntryCounter
END
GO
Related
I have a SQL Trigger on a table that works... most of the time. And I cannot figure out why sometimes the fields are NULL
The trigger works by Updateing the LastUpdateTime whenever something is modified in the field, and the InsertDatetime when first Created.
For some reason this only seems to work some times.
ALTER TRIGGER [dbo].[DateTriggerTheatreListHeaders]
ON [dbo].[TheatreListHeaders]
AFTER INSERT,UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF NOT EXISTS(SELECT * FROM DELETED)
BEGIN
UPDATE ES
SET InsertDatetime = Getdate()
,LastUpdateDateTime = Getdate()
FROM TheatreListHeaders es
JOIN Inserted I ON es.UNIQUETHEATRELISTNUMBER = I.UNIQUETHEATRELISTNUMBER
END
IF UPDATE(LastUpdateDateTime) OR UPDATE(InsertDatetime)
RETURN;
IF EXISTS (
SELECT
*
FROM
INSERTED I
JOIN
DELETED D
-- make sure to compare inserted with (same) deleted person
ON D.UNIQUETHEATRELISTNUMBER = I.UNIQUETHEATRELISTNUMBER
)
BEGIN
UPDATE ES
SET InsertDatetime = ISNULL(es.Insertdatetime,Getdate())
,LastUpdateDateTime = Getdate()
FROM TheatreListHeaders es
JOIN Inserted I ON es.UNIQUETHEATRELISTNUMBER = I.UNIQUETHEATRELISTNUMBER
END
END
A much simpler and efficient approach to do what you are trying to do, would be something like...
ALTER TRIGGER [dbo].[DateTriggerTheatreListHeaders]
ON [dbo].[TheatreListHeaders]
AFTER INSERT,UPDATE
AS
BEGIN
SET NOCOUNT ON;
--Determine if this is an INSERT OR UPDATE Action .
DECLARE #Action as char(1);
SET #Action = (CASE WHEN EXISTS(SELECT * FROM INSERTED)
AND EXISTS(SELECT * FROM DELETED)
THEN 'U' -- Set Action to Updated.
WHEN EXISTS(SELECT * FROM INSERTED)
THEN 'I' -- Set Action to Insert.
END);
UPDATE ES
SET InsertDatetime = CASE WHEN #Action = 'U'
THEN ISNULL(es.Insertdatetime,Getdate())
ELSE Getdate()
END
,LastUpdateDateTime = Getdate()
FROM TheatreListHeaders es
JOIN Inserted I ON es.UNIQUETHEATRELISTNUMBER = I.UNIQUETHEATRELISTNUMBER;
END
"If update()" is poorly defined/implemented in sql server IMO. It does not do what is implied. The function only determines if the column was set by a value in the triggering statement. For an insert, every column is implicitly (if not explicitly) assigned a value. Therefore it is not useful in an insert trigger and difficult to use in a single trigger that supports both inserts and updates. Sometimes it is better to write separate triggers.
Are you aware of recursive triggers? An insert statement will execute your trigger which updates the same table. This causes the trigger to execute again, etc. Is the (database) recursive trigger option off (which is typical) or adjust your logic to support that?
What are your expectations for the insert/update/merge statements against this table? This goes back to your requirements. Is the trigger to ignore any attempt to set the datetime columns directly and set them within the trigger always?
And lastly, what exactly does "works sometimes" actually mean? Do you have a test case that reproduces your issue. If you don't, then you can't really "fix" the logic without a specific failure case. But the above comments should give you sufficient clues. To be honest, your logic seems to be overly complicated. I'll add that it also is logically flawed in the way that it set insertdatetime to getdate if the existing value is null during an update. IMO, it should reject any update that attempts to set the value to null because that is overwriting a fact that should never change. M.Ali has provided an example that is usable but includes the created timestamp problem. Below is an example that demonstrates a different path (assuming the recursive trigger option is off). It does not include the rejection logic - which you should consider. Notice the output of the merge execution carefully.
use tempdb;
set nocount on;
go
create table zork (id integer identity(1, 1) not null primary key,
descr varchar(20) not null default('zippy'),
created datetime null, modified datetime null);
go
create trigger zorktgr on zork for insert, update as
begin
declare #rc int = ##rowcount;
if #rc = 0 return;
set nocount on;
if update(created)
select 'created column updated', #rc as rc;
else
select 'created column NOT updated', #rc as rc;
if exists (select * from deleted) -- update :: do not rely on ##rowcount
update zork set modified = getdate()
where exists (select * from inserted as ins where ins.id = zork.id);
else
update zork set created = getdate(), modified = getdate()
where exists (select * from inserted as ins where ins.id = zork.id);
end;
go
insert zork default values;
select * from zork;
insert zork (descr) values ('bonk');
select * from zork;
update zork set created = null, descr = 'upd #1' where id = 1;
select * from zork;
update zork set descr = 'upd #2' where id = 1;
select * from zork;
waitfor delay '00:00:02';
merge zork as tgt
using (select 1 as id, 'zippity' as descr union all select 5, 'who me?') as src
on tgt.id = src.id
when matched then update set descr = src.descr
when not matched then insert (descr) values (src.descr)
;
select * from zork;
go
drop table zork;
I'm new to SQL Server, and I'm trying to build a simple update trigger that writes a row to a staging table whenever the column ceu_amount is updated from zero to any number greater than zero.
From using PRINT statements, I know that the variables are containing the correct values to execute the INSERT statement, but no rows are being inserted.
Can you help?
CREATE TRIGGER [dbo].[TRG_Product_Function_Modified] ON [dbo].[Product_Function]
AFTER UPDATE
AS
BEGIN
SET NOCOUNT ON;
--
-- Variable definitions
--
DECLARE #product_code_new as varchar(31)
DECLARE #product_code_old as varchar(31)
--
-- Check if the staging table needs to be updated.
--
SELECT #product_code_new = product_code FROM Inserted where ISNULL(ceu_amount,0) > 0;
SELECT #product_code_old = product_code FROM Deleted where ISNULL(ceu_amount,0) = 0;
IF #product_code_new IS NOT NULL
AND #product_code_old IS NOT NULL
INSERT INTO Product_Function_Staging VALUES (#product_code_new,CURRENT_TIMESTAMP);
END;
This part of code looks suspicious to me..
SELECT #product_code_new = product_code FROM Inserted where ISNULL(ceu_amount,0) > 0;
SELECT #product_code_old = product_code FROM Deleted where ISNULL(ceu_amount,0) = 0;
IF #product_code_new IS NOT NULL
AND #product_code_old IS NOT NULL
INSERT INTO Product_Function_Staging VALUES (#product_code_new,CURRENT_TIMESTAMP);
The above will work fine ,if there is only one row updated,what if there is more than one value..the product_code will default to last value
You can change the above part of code to below
Insert into Product_Function_Staging
select product_code ,CURRENT_TIMESTAMP from inserted where product_code is not null
You will get undetermined values for #product_code_new if there are more than one rows updated with ceu_amount>0; Similar for #product_code_old if more than one rows updated with ceu_amount NULL or equal 0.
Can you post some sample data?
I would not use variables like that in a trigger, since what causes the trigger could be an update to more than one row, at which point you would have multiple rows in your updated and deleted tables.
I think we can more safely and efficiently make this insert with one simple query, though I'm assuming you have a unique key to use:
CREATE TRIGGER [dbo].[TRG_Product_Function_Modified] ON [dbo].[Product_Function]
AFTER UPDATE
AS
BEGIN
SET NOCOUNT ON;
INSERT INTO Product_Function_Staging
SELECT i.product_code, CURRENT_TIMESTAMP
FROM inserted i
JOIN deleted d ON i.product_code = d.product_code -- assuming product_code is unique
WHERE i.ceu_amount > 0 -- new value > 0
AND ISNULL(d.ceu_amount, 0) = 0; -- old value null or 0
END;
I'm not sure where you need to check for nulls in your data, so I've made a best guess in the where clause.
Try using this
CREATE TRIGGER [dbo].[Customer_UPDATE]
ON [dbo].[Customers]
AFTER UPDATE
AS
BEGIN
SET NOCOUNT ON;
DECLARE #CustomerId INT
DECLARE #Action VARCHAR(50)
SELECT #CustomerId = INSERTED.CustomerId
FROM INSERTED
IF UPDATE(Name)
BEGIN
SET #Action = 'Updated Name'
END
IF UPDATE(Country)
BEGIN
SET #Action = 'Updated Country'
END
INSERT INTO CustomerLogs
VALUES(#CustomerId, #Action)
END
I'm trying to create one trigger for insert,delete and update on customers table.
Trigger was created successfully ,however, I'm sure it contains many errors.
Here is my code of trigger
go
create trigger Onetrig
on customers
after update,insert,delete
as
declare #log varchar(100),#name varchar(20),#activity varchar(20)
begin
if exists(select * from deleted) and exists(select * from deleted)
set #activity = 'Update'
set #name = (select c_name from inserted)
set #log = 'Record Updated in database '+#name
insert into logs
values(#activity,#log,GETDATE())
if exists(select * from inserted) and not exists(select * from deleted)
set #activity = 'Insert'
set #name = (select c_name from inserted)
set #log = 'Record Inserted in database '+#name
insert into logs
values(#activity,#log,GETDATE())
if exists(select * from deleted) and not exists(select * from inserted)
set #activity = 'Insert'
set #name = (select c_name from deleted)
set #log = 'Record Deleted from database '+#name
insert into logs
values(#activity,#log,GETDATE())
end
My task is to populate the log table with the activities of these three operations. when I perform any of the three operations it throws error of some kind of conversion.
Msg 8152, Level 16, State 14, Procedure Onetrig, Line 11
String or binary data would be truncated.
The statement has been terminated.
customers table has some records.
Here is the code of my customers & log table:
create table logs
(activity varchar(20),report varchar(20),Time datetime)
create table customers
(c_id int primary key identity(1,1) NOT NULL,c_name varchar(20),c_lastname varchar(20))
What conversion am I missing?
You have declared report to be 20 characters in logs. But, you are inserting the string 'Record Updated in database '+#name into it. This has at least 27 characters.
Suggestions:
Fix the length of the varchar fields. You might as well make them much longer, even up to 8000 characters.
When doing insert, always include the list of columns explicitly.
Fix the first if statement to refer to inserted and deleted, so the logic makes sense.
Put semicolons at the end of each statement.
Gordon Linoff's answer is very good.
I would like to add that in case of trigger, following lines
set #name = (select c_name from inserted)
set #name = (select c_name from deleted)
assume that there is always only one row inserted / deleted / updated. Which is wrong because DML triggers are at statement level not at row level.
I would change (for I/U/D) thus:
if exists ...
begin
set #activity = 'U/I/D'
insert into dbo.logs (... columns ...) -- <-- You should use the schema (default schema is dbo)
select #activity, 'Record Updated in database ' + x.c_name, GETDATE()
-- ^
-- |
-- ----------------------------------------------------------
-- The maximum length of dbo.logs.c_name (!?) column should be
-- LEN('Record Updated in database') + 1 + MaxLength of dbo.customers.c_name column
from inserted as x -- or deleted
end
I have to have one single trigger that fires on either the UPDATE OR DELETE operations. I have the trigger working fine for when one certain column is updated. However, I need different logic for when a DELETE operation was fired. How would I have both logic inside of one trigger? Here is what I have so far:
ALTER TRIGGER [dbo].[Audit_Emp_Trigger]
ON [dbo].[EMPLOYEE]
AFTER UPDATE, DELETE
AS
BEGIN
--Only execute the trigger if the Dno field was updated or deleted
IF UPDATE(Dno)
BEGIN
--If the Audit_Emp_Record table does not exist already, we need to create it
IF OBJECT_ID('dbo.Audit_Emp_Record') IS NULL
BEGIN
--Table does not exist in database, so create table
CREATE TABLE Audit_Emp_Record
(
date_of_change smalldatetime,
old_Lname varchar (50),
new_Lname varchar (50),
old_ssn int,
new_ssn int,
old_dno int,
new_dno int
);
--Once table is created, insert the values of the update operation into the table
INSERT INTO Audit_Emp_Record(date_of_change, old_Lname, new_Lname, old_ssn, new_ssn, old_dno, new_dno) SELECT GETDATE(), D.Lname, I.Lname, D.Ssn, I.Ssn, D.Dno, I.Dno FROM inserted I JOIN deleted D ON I.Ssn = D.Ssn
END
ELSE
BEGIN
--The table already exists, so simply insert the new values of the update operation into the table
INSERT INTO Audit_Emp_Record(date_of_change, old_Lname, new_Lname, old_ssn, new_ssn, old_dno, new_dno) SELECT GETDATE(), D.Lname, I.Lname, D.Ssn, I.Ssn, D.Dno, I.Dno FROM inserted I JOIN deleted D ON I.Ssn = D.Ssn
END
END
END
You can test for the type of operation by seeing which of the magic-/pseudo-tables -- INSERTED and DELETED have data in them. I prefer to use something like the following:
DECLARE #Operation CHAR(1);
IF (EXISTS(SELECT * FROM inserted))
BEGIN
IF (EXISTS(SELECT * FROM deleted))
BEGIN
-- rows in both has to be an UPDATE
SET #Operation = 'U';
END;
ELSE
BEGIN
-- no rows in "deleted" has to be an INSERT
SET #Operation = 'I';
END;
END;
ELSE
BEGIN
-- no rows in "inserted" has to be a DELETE
SET #Operation = 'D';
END;
You can then use the #Operation variable in an IF statement to do one or the other of those operations.
Something like:
IF (#Operation = 'U')
BEGIN
--Only execute the trigger if the Dno field was updated or deleted
IF UPDATE(Dno)
BEGIN
{your current code here}
END;
END;
ELSE
BEGIN
{what to do if the operation is a DELETE goes here}
END;
Technically you don't need the ELSE condition that sets #Operation = 'I';, but if you are going to copy/paste this code into various triggers or keep around as a template then no harm in it handling all three conditions.
Also, just as a side-note, you don't need the ELSE condition of the IF OBJECT_ID('dbo.Audit_Emp_Record') IS NULL statement, nor the INSERT INTO Audit_Emp_Record that is just after the CREATE TABLE but before the END. Just do the CREATE TABLE if it doesn't exist and then do the INSERT outside of that test. Meaning:
IF UPDATE(Dno)
BEGIN
--If the Audit_Emp_Record table does not exist already, we need to create it
IF OBJECT_ID('dbo.Audit_Emp_Record') IS NULL
BEGIN
--Table does not exist in database, so create table
CREATE TABLE Audit_Emp_Record
...
END
INSERT INTO Audit_Emp_Record(...)
END
I'm trying to create a trigger that initialises a record over multiple tables when a master record is inserted to a master table. The code below gives the error "Object reference not set to an instance of an object."
Appraisal is the table the trigger exists for and every table concerned has an AppraisalID foreign key.
BEGIN TRANSACTION
DECLARE #appraisalid int
SET #appraisalid = (SELECT AppraisalID FROM inserted)
INSERT INTO dbo.AppraisalCPD (AppraisalID)
VALUES (#appraisalid)
COMMIT;
The code below works, but I would rather use a variable to assign the value as I need to add rows to a fair few tables.
BEGIN
INSERT INTO dbo.AppraisalCPD
(AppraisalID)
SELECT AppraisalID
FROM inserted;
END;
If anyone can suggest a way to set an appraisalid variable using the inserted row in the Appraisal table to insert rows into every other table I need to, that'd be very helpful.
I am assuming you are talking about home appraisal.
The [appraisal] table is the parent and the [owners]/[location] are the children.
Here is a play schema in tempdb.
-- just playing
use tempdb;
go
-- drop table
if object_id('appraisal') > 0
drop table appraisal
go
-- create table - home appraisal
create table appraisal
(
app_id int identity (1,1),
app_request datetime,
app_employee_id int
);
-- drop table
if object_id('owners') > 0
drop table owners
go
-- create table - the owners
create table owners
(
own_id int identity (1,1) primary key,
own_first_nm varchar(64),
own_last_nm varchar(64),
app_id int
);
-- drop table
if object_id('location') > 0
drop table location
go
-- the location
create table location
(
loc_id int identity (1,1) primary key,
loc_street varchar(64),
loc_city varchar(64),
loc_state varchar(2),
loc_zip varchar(9),
app_id int
);
go
When creating empty child records via a trigger, you either have to define default values or supply them in the trigger.
Also, I leave setting up foreign keys for you to handle.
The code for the trigger could look like the following.
-- The trigger
CREATE TRIGGER DBO.make_empty_children on dbo.appraisal
for insert, update, delete
as
BEGIN
-- nothing to do?
IF (##rowcount = 0) RETURN;
-- do not count rows
SET NOCOUNT ON;
-- delete
IF NOT EXISTS (SELECT * FROM inserted)
BEGIN
RETURN;
END
-- insert
ELSE IF NOT EXISTS (SELECT * FROM deleted)
BEGIN
-- dummy record for owners
insert into owners
(
own_first_nm,
own_last_nm,
app_id
)
select
'enter first name',
'enter last name',
app_id
from
inserted;
-- dummy record for location
insert into location
(
loc_street,
loc_city,
loc_state,
loc_zip,
app_id
)
select
'enter street',
'enter city',
'ri',
'00000',
app_id
from
inserted;
RETURN;
END
-- update
ELSE
BEGIN
RETURN;
END
END
GO
I left place holders for DELETE and UPDATE operations.
1 - Do you want to reject updates to the id (key) in the appraisal table. Probably not. This can also be taken care (prevented) of by a Foreign Key (FK).
2 - Do you want to cascade deletes? This also can be handled by a FK or in code in the trigger.
Lets see no records in the tables.
select * from appraisal;
select * from owners;
select * from location;
Like Marc / Aaron said, the inserted / deleted tables are record sets. Not a single row.
Order is not guaranteed. Use an order by if you want the records inserted by app id order.
-- Insert 2 records
insert into appraisal
(
app_request,
app_employee_id
)
values
(getdate(), 7),
(dateadd(d, 1, getdate()), 7);
-- Lets see the data
select * from appraisal;
select * from owners;
select * from location;