This is an hypothetical case..
I'm trying to find a good approach to make sure that every value inserted in an specific column col1 of my table mytable has a specific string http:// at the begining of the value.
Example:
I want to insert myprofile into mytable so (after my check condition..) the final value would be http://myprofile
I guess that a good approach could be using a trigger on insert but I didn't find anything concrete yet..
Any ideas?
Thank you.
You can try something like this as a starting point - this is for SQL Server (don't know MySQL well enough to provide that trigger code for you):
-- create the trigger, give it a meaningful name
CREATE TRIGGER PrependHttpPrefix
ON dbo.YourTableName -- it's on a specific table
AFTER INSERT, UPDATE -- it's for a specific operation, or several
AS
BEGIN
-- the newly inserted rows are stored in the "Inserted" pseudo table.
-- It has the exact same structure as your table that this trigger is
-- attached to.
-- SQL Server works in such a way that if the INSERT affected multiple
-- rows, the trigger is called *once* and "Inserted" contains those
-- multiple rows - you need to work with "Inserted" as a multi-row data set
--
-- You need to join the "Inserted" rows to your table (based on the
-- primary key for the table); for those rows newly inserted that
-- **do not** start with "http://" in "YourColumn", you need to set
-- that column value to the fixed text "http:/" plus whatever has been inserted
UPDATE tbl
SET YourColumn = 'http://' + i.YourColumn
FROM dbo.YourTableName tbl
INNER JOIN Inserted i ON tbl.PKColumn = i.PKColumn
WHERE LEFT(i.YourColumn, 7) <> 'http://'
END
Related
When insert I need edit a value if it is null. I create a trigger but I don't know how to edit inserted table.
ALTER TRIGGER [trigger1] on [dbo].[table]
instead of insert
as
declare #secuencia bigint, #ID_PERSONA VARCHAR;
select #secuencia = SECUENCIA from inserted
select #ID_PERSONA = ID_PERSONA from inserted
if #secuencia is null begin
set inserted.SECUENCIA = NEXT VALUE FOR SEQ_BIOINTEG --(Sequence)
end
i dont know how to edit inserted table.
You do not. That table is read only.
Note how your trigger also says:
instead of insert
There is no way to edit the inserted table.
What you do instead, is setting up an INSERT command for the original table, using the data from the inserted table to filter to the ROWS of inserted - mostly by a join.
Changing inserted makes no sense, logically - because triggers in SQL are one of two things:
INSTEAD OF - then there is no actual insert happening for inserted to start with. Instead of doing the insert, the trigger is called. As such, changing inserted - makes no sense.
AFTER - then the insert already happened (and you UPDATE the rows). As the trigger runs after the update, changing inserting makes no sense.
Note that I say ROWS - your trigger has one very basic error: it assumes inerted contains ONE row. It is a table - it is possible the changes come from an insert statement that inserts multiple rows (which is trivial, i.e. select into, or simply an insert with values for multiple rows). Handle those.
select #ID_PERSONA = ID_PERSONA from inserted
Makes NO sense - inserted is a table, so ID_PERSONA from inserted contains what value, if 2 rows are inserted? You must treat inserted like any other table.
Apart from all the varied issues with your trigger code, as mentioned by others, the easiest way to use a SEQUENCE value in a table is to just put it in a DEFAULT constraint:
ALTER TABLE dbo.[table]
ADD CONSTRAINT DF_table_seq
DEFAULT (NEXT VALUE FOR dbo.SEQ_BIOINTEG)
FOR SECUENCIA;
I have never really worked with Triggers before in MSSQL but I think it'll be what I need for this task.
The structure of the table is as such:
ID|****|****|****|****|****|****|****|TOUROPERATOR
The Tour Operator Code is the code that tells us what company owned the flight we carried out for them. Two of those codes (there are 24 in total) are outdated. Our users requested that those two be changed but the tour operator code is pulled from a database we don't control. The FlightData table however, we do control. So I was thinking a trigger could change the tour operator code if it was one of the two outdated ones, to the correct ones instead respectively when they were inserted.
So I went into good ol' SQL Management Studio and asked to make a trigger. It gave me some sample code and here is my Pseudo Code below:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER ChangeProvider
ON FlightData
AFTER INSERT
AS
BEGIN
IF(TheInsertedValue == Criteria)
UPDATE FlightData
SET TheInsertedValue = NewValue
ENDIF
END
GO
I am not that good with this type of Database Programming so excuse my mistakes.
How would I go about doing this?
You could add a computed column to your table instead of adding a trigger.
Then the new column could just use a case statement to either show
the original TourOperator column value or the new value you wanted.
You'd add a new column to your table like this
TourOperatorCorrect = CASE WHEN TourOperator = 'Whatever value' THEN 'ChangedValue'
--I just want to use what I have already in the TourOperator column
ELSE TourOperator
END AS VARCHAR(50)
Basics of computed columns are here - https://msdn.microsoft.com/en-ie/library/ms188300.aspx
Your misconception here is that the trigger runs once per inserted value - it is in fact run once per insert statement, so you can and will find more than one row inserted at once.
You'll find that your inserted values are in the pseudo table inserted, which has the same structure as your FlightData table in this case. You write a select statement against that, specifying any criteria you wish.
However, it's not immediately clear what your logic is - does the FlightData table you are updating in your trigger only have one row? Do you update every row in the table with the newest inserted value? It is hard to understand what you are trying to now, and what the purpose of the table and this trigger are - let alone what you would want to do if you inserted more than one row at once.
When inserted table contains mutiple rows,your code will fail,so change code to work with inserted table as whole
UPDATE F
SET f.TheInsertedValue = i.value
from inserted i
join
Flighttable F
on f.matchingcolumn=i.matchingcolumn
and i.somevalue='criteria'
I want to delete new record if the same record created before.
My columns are date, time and MsgLog. If date and time are same, I want to delete new one.
I need help .
You can check in the table whether that value exists or not in the column using a query. If it exists, you can show message that a record already exists.
To prevent such kind of erroneous additions you can add restriction to your table to ensure unique #Date #Time pairs; if you don't want to change data structure (e.g. you want to add records with such restrictions once or twice) you can exploit insert select counstruction.
-- MS SQL version, check your DBMS
insert into MyTable(
Date,
Time,
MsgLog)
select #Date,
#Time,
#MsgLog
where not exists(
select 1
from MyTable
where (#Date = Date) and
(#Time = Time)
)
P.S. want to delete new one equals to do not insert new one
You should create a unique constraint in the DB level to avoid invalid data no matter who writes to your DB.
It's always important to have your schema well defined. That way you're safe that no matter how many apps are using your DB or even in case someone just writes some inserts manually.
I don't know which DB are you using but in MySQL can use to following DDL
alter table MY_TABLE add unique index(date, time);
And in Oracle you can :
alter table MY_TABLE ADD CONSTRAINT constaint_name UNIQUE (date, time);
That said, you can also (not instead of) do some checks before inserting new values to avoid dealing with exceptions or to improve performance by avoiding making unnecessary access to your DB (length \ nulls for example could easily be dealt with in the application level).
You can avoid deleting by checking for duplicate while inserting.
Just modify your insert procedure like this, so no duplicates will entered.
declare #intCount as int;
select #intCount =count(MsgLog) where (date=#date) and (time =#time )
if #intCount=0
begin
'insert procedure
end
> Edited
since what you wanted is you need to delete the duplicate entries after your bulk insert. Think about this logic,
create a temporary table
Insert LogId,date,time from your table to the temp table order by date,time
now declare four variables, #preTime,#PreDate,#CurrTime,#CurrDate
Loop for each items in temp table, like this
while
begin
#pkLogID= ' Get LogID for the current row
select #currTime=time,#currDate=date from tblTemp where pkLogId=#pkLogID 'Assign Current values
'Delete condition check
if (#currDate=#preDate) and (#currTime=#preTime)
begin
delete from MAINTABLE where pkLogId=#pkLogID
end
select #preDate=#currDate,#preTime=#currTime 'Assign current values as preValues for next entries
end
The above strategy is we sorted all entries according to date and time, so duplicates will come closer, and we started to compare each entry with its previous, when match found we deleting the duplicate entry.
Suppose I have tables T1 and T2
Columns of T1 -->Value
Columns of T2 -->OldValue NewValue
What I require is a trigger which will insert a record in T2 on updation of T1 , I need to know the old value and new value also , I have never used triggers before , so can any help me with this , how do I go about creating this trigger.Is it possible ,thanks.
Well, you start writing a trigger with CREATE TRIGGER:
CREATE TRIGGER NameOfTheTriggerPlease
…
The table that should trigger the additional action is T1 so the trigger should be defined ON that table:
CREATE TRIGGER T1OnUpdate /* that's just an example,
you can use a different name */
ON T1
…
The action that the trigger should be invoked on is UPDATE and the timing is AFTER the update, so…
CREATE TRIGGER T1OnUpdate
ON T1
AFTER UPDATE
…
Now's the time to introduce the body of the trigger, i.e. the statements that should actually be executed by the trigger. You introduce the body with the AS keyword followed by the statements themselves.
In your case, there would be just one statement, INSERT, which is obvious. What's not so obvious is how we are going to access the old and the new values. Now, SQL Server offers you two virtual tables, INSERTED and DELETED, and you can easily guess that the former contains all the new values and the latter the old ones.
These tables have the same structure as the table the trigger is assigned to, i.e. T1. They only contain rows that were affected by the particular UPDATE statement that invoked the trigger, which means there may be more than one. And that, in turn, means that you need to have some primary key or a unique column (or a set of columns) in your T1 table that you can use in the trigger to match deleted and inserted rows. (In fact, you might also need your T2 table to have a column that would reference the T1's primary key, so you could later establish which row of T1 had which values stored in T2.)
For the purposes of this answer, I'm going to assume that there's a primary key column called PK and a foreign key column of the same name in T2. And the INSERT statement then might look like this:
CREATE TRIGGER T1OnUpdate
ON T1
AFTER UPDATE
AS
INSERT INTO T2 (PK, OldValue, NewValue)
SELECT i.PK, i.Value, d.Value
FROM INSERTED i INNER JOIN DELETED d ON i.PK = d.PK
One last (but not least) thing to remember: the entire CREATE TRIGGER statement should be the only one in the batch, i.e. there should be no statements preceding the CREATE TRIGGER keywords (but you can put comments there) and, likewise, everything after the AS keyword is considered part of the trigger's body (but you can put the GO delimiter to indicate the end of the statement if you are running the script in SQL Server Management Studio, for instance).
Useful reading:
CREATE TRIGGER (Transact-SQL)
I'm not going to build the whole thing for you (no fun, right?) but I can point you in the right direction
create trigger logUpdate
on T1
After update
as
begin
insert into T2...
--here is just an example
select * from deleted --the DELETED table contains the OLD values
select * from inserted --the INSERTED table contains the NEW values
end
remember that DELETED and INSERTED are internal tables that contains old and new values. On a update trigger, they both exist. On a insert trigger, DELETED will be null because there is nothing being delete. Same logic on a delete trigger, the INSERTED will be empty
EDIT:
answering your question: no matter how many fields you update, your DELETED and INSERTED tables you have all the columns of all the rows affected. Of course, if you update only one column, all the other will have the same value on DELETED and INSERTED
create trigger T_UPD_T1
on T1 FOR update
as
insert into T2 select deleted.value, inserted.value from inserted, deleted
I wish to make a trigger but i'm not sure how to grab the data for whatever caused the trigger.
I have a simlpe table.
FooId INT PK NOT NULL IDENTITY
Name VARCHAR(100) NOT NULL
I wish to have a trigger so that when an UPDATE, INSERT or DELETE occurs, i then do the following.
Pseduocode
IF INSERT
Print 'Insert' & Name
ELSE IF UPDATE
Print 'Update' & FooId & Name
ELSE IF DELETE
Print 'Delete' & FooId & Name
Now, I know how to make a trigger for a table.
What i don't know how to do is figure out the values based on what the trigger type is.
Can anyone help?
Edit: Not sure if it helps, but db is Sql Server 2008
the pseudo table "inserted" contains the new data, and "deleted" table contains the old data.
You can do something like
create trigger mytrigger on mytable for insert, update, delete
as
if ( select count(*) from inserted ) > 0
-- insert or update
select FooId, Name from inserted
else
-- delete
select FooId, Name from deleted
To clarify all the comments made by others, on an insert, the inserted table contains data and deleted is empty. On a delete, the situation is reversed. On an update, deleted and inserted contain the "before" and "after" copy of any updated rows.
When you are writing a trigger, you have to account for the fact that your trigger may be called by a statement that effects more than one row at a time.
As others have pointed out, you reference the inserted table to get the values of new values of updated or inserted rows, and you reference the deleted table to get the value of deleted rows.
SQL triggers provide an implicitly-defined table called "inserted" which returns the affected rows, allowing you to do things like
UPDATE mytable SET mytimestamp = GETDATE() WHERE id IN (SELECT id FROM inserted)
Regarding your code sample, you'll want to create separate INSERT, UPDATE and DELETE triggers if you are performing separate actions for each.
(At least, this is the case in SQL Server... you didn't specify a platform.)
On 2008, there is also MERGE command. How do you want to handle it?
Starting from 2008, there are four commands you can modify a table with:
INSERT, UPDATE, DELETE, and MERGE:
http://blogs.conchango.com/davidportas/archive/2007/11/14/SQL-Server-2008-MERGE.aspx
http://sqlblogcasts.com/blogs/grumpyolddba/archive/2009/03/11/reasons-to-move-to-sql-2008-merge.aspx
What do you want your trigger to do when someone issues a MERGE command against your table?