I have a table called Army.There are the attributes:
army
army_name VARCHAR(50) PRIMARY KEY
number_of_soliders INTEGER;
I need to convert number_of_soliders to 0 after inserting to this table (or allow only 0 to be inserted).
How to accomplish this?
Since this is part of a school project, you need to use a CREATE TRIGGER statement and modify the value BEFORE INSERT ON army and do that FOR EACH ROW.
In the trigger's PL/SQL block, you need to use the :new record and set the number_of_soldiers attribute to be zero using :NEW.number_of_soldiers := 0;.
The documentation for CREATE TRIGGER is here.
You can try altering the column and set default value as 0.
So, when you insert army_name, the row will by default have number_of_soliders as 0.
ALTER TABLE ARMY MODIFY number_of_soliders default 0;
Related
create or replace NONEDITIONABLE TRIGGER SumUpdate AFTER INSERT ON stavkaotpremnice FOR EACH ROW
declare pragma autonomous_transaction;
begin
UPDATE otpremnica a
set a.ukupno=
(SELECT SUM(ukupno)
FROM stavkaotpremnice
WHERE brojotpremnice =: new.brojotpremnice)
WHERE a.brojotpremnice = :new.brojotpremnice;
commit;
end;
This trigger is to sum values of a column called "ukupno" in table stavakaotpremnice then store it in another table otpremnica in a column also called "ukupno".
The trigger check if the id(brojotpremnice) is the same and make the sum.
Brojotpremnice is a foreign key from table otpremnica.
Does anyone know why it is totally ignoring the first entry?
If i put rows in stavkaotpremnica i just count the first entry.
This type of problem can be solved via incremental addition as follows:
UPDATE otpremnica a
set a.ukupno = a.ukupno + :new.ukupno
WHERE a.brojotpremnice = :new.brojotpremnice;
Also, please read about pragma autonomous_transaction. Why it is used? Intentional? If you have no idea, read it. (It separates the transaction)
I am trying to write a trigger in SAP HANA to update a field of a table when new records are being inserted to that table. Following is a sample trigger that I have written.
CREATE TRIGGER SAMPLE
AFTER INSERT ON TARGET_TABLE
REFERENCING NEW ROW NEW_ROW
FOR EACH ROW
BEGIN
UPDATE TARGET_TABLE SET VALID_FROM='2018-02-01' WHERE ITEM=:NEW_ROW.ITEM
END
When I try this, I get the error:
Modification of subject table in trigger not allowed
Is there a way by which I can achieve this?
This suggests to use the transition variable NEW_ROW, appreciate if a code sample can be provided.
You don't actually need to create trigger for your requirement as I can see from your post (of course if it is only updating a date field)
You can define the VALID_FROM column with a DEFAULT value
For example,
Create Column Table DefaultColumnTable (
Id int,
Code varchar(5),
VALID_FROM date default '2018-02-01'
)
So whenever a new row is inserted, unless an alternative value is stated the valid_from column will be populated with default date specified in the DDL command above.
The users can change the valid_from field value without any problem
#Kalpa, maybe you can use BEFORE INSERT Trigger
Please check following sample
create trigger TriggerTable_B_INS BEFORE INSERT on TriggerTable
REFERENCING NEW ROW mynewrow
FOR EACH ROW
begin
declare lv_d date;
lv_d := '20180201';
mynewrow.VALID_FROM = :lv_d;
end;
You set only the new row columns before Insert command executes over the target table.
You don't explicitly execute an INSERT command, just set new values for new row columns. That's all
I hope it helps
I have a table names Locations. It has columns [ID, GUID_ID, NAME, GEOMETRY]. I want to update GUID_ID column after a row inserted. So I will create a trigger to do this.
CREATE TRIGGER update_id
AFTER INSERT ON Locations
?? (How can Update GUID_ID column as uuid_generate_v4())
I set a default value for this column. But third party applications like QGIS inserts thousands of geometry records at same time. So the default value does not fill all columns. They are null. So I need trigger for solution.
I think it dosnt matter how much records QGIS enters, if you have defined a default value for field. May be QGIS is entering empty space instead. You can also add "NOT NULL" constraint in the field definition.
However trigger can be used like this. I am setting the GUID_ID value BEFORE INSERTING though.
CREATE TRIGGER update_id
BEFORE INSERT ON Locations
FOR EACH ROW EXECUTE PROCEDURE fn_trgr();
CREATE OR REPLACE FUNCTION fn_trgr() RETURNS TRIGGER AS $$
BEGIN
IF pg_trigger_depth() <> 1 THEN
RETURN NEW;
END IF;
NEW.GUID_ID = uuid_generate_v4(); -- or whatever value you wants to set
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
I have a table with the following column:
NOTEID NUMBER NOT NULL,
For all intents and purposes, this column is the primary key. This table has a few thousand rows, each with a unique ID. Before, the application would SELECT the MAX() value from the table, add one, then use that as the next value. This is a horrible solution, and is not transaction or thread safe (in fact, before they didn't even have a UNIQUE constraint on the column and I could see the same NOTEID was duplicated in 9 different occasions)..
I'm rather new to Oracle, so I'd like to know the best syntax to ALTER this table and make this column auto-increment instead. If possible, I'd like to make the next value in the sequence be the MAX(NOTEID) + 1 in the table, or just make it 800 or something to start out. Thanks!
You can't alter the table. Oracle doesn't support declarative auto-incrementing columns. You can create a sequence
CREATE SEQUENCE note_seq
START WITH 800
INCREMENT BY 1
CACHE 100;
Then, you can create a trigger
CREATE OR REPLACE TRIGGER populate_note_id
BEFORE INSERT ON note
FOR EACH ROW
BEGIN
:new.note_id := note_seq.nextval;
END;
or, if you want to allow callers to specify a non-default NOTE_ID
CREATE OR REPLACE TRIGGER populate_note_id
BEFORE INSERT ON note
FOR EACH ROW
BEGIN
IF( :new.note_id is null )
THEN
:new.note_id := note_seq.nextval;
END IF;
END;
If your MAX(noteid) is 799, then try:
CREATE SEQUENCE noteseq
START WITH 800
INCREMENT BY 1
Then when inserting a new record, for the NOTEID column, you would do:
noteseq.nextval
I have been looking for a way to define an autoincrement data type in Oracle and have found these questions on Stack Overflow:
Autoincrement in Oracle
Autoincrement Primary key in Oracle database
The way to use autoincrement types consists in defining a sequence and a trigger to make insertion transparent, where the insertion trigger looks so:
create trigger mytable_trg
before insert on mytable
for each row
when (new.id is null)
begin
select myseq.nextval into :new.id from dual;
end;
I have some doubts about the behaviour of this trigger:
What does this trigger do when the supplied value of "id" is different from NULL?
What does the colon before "new" mean?
I want the trigger to insert the new row with the next value of the sequence as ID whatever the supplied value of "new.id" is. I imagine that the WHEN statement makes the trigger to only insert the new row if the supplied ID is NULL (and it will not insert, or will fail, otherwise).
Could I just remove the WHEN statement in order for the trigger to always insert using the next value of the sequence?
The WHEN condition specifies a condition that must be TRUE for the trigger to fire. In this exampple, the trigger will only fire if the new row has a NULL IS. When the ID is not null, the trigger will not fire and so whatever value ID has been given in the insert statement will be left alone.
Yes, if you simply remove the WHEN condition then the trigger will always fire and so will always provide a sequence value for ID.
Nothing. That allows to specify a value manually.
It's a placeholder for the new value of the column.
You have 2 methods you can do:
if the table looks like this:
create table my_test (
id number,
my_test data varchar2(255)
);
and your sequence is this:
create sequence test_seq
start with 1
increment by 1
nomaxvalue;
you can create a trigger like this (with no When statement like Tony Andrews said)
create trigger test_trigger
before insert on my_test
for each row
begin
select test_seq.nextval into :new.id from dual;
end;
or you could just simply use this then you don't need a trigger:
insert into my_test values(test_seq.nextval, 'voila!');