I have a trigger:
create or replace trigger trig
before insert on sistem
for each row
declare
v_orta number;
begin
SELECT v_orta INTO :new.orta_qiymet
FROM sistem;
v_orta:=(:new.riyaziyyat+:new.fizika)/2;
insert into sistem(orta_qiymet)
values(v_orta);
end trig;
When I insert a row:
insert into sistem(riyaziyyat,fizika) values(4,4)
I get an error:
Why am I getting that error?
This is fundamentally not understanding how triggers work. You can't generally select from the table the trigger is against, and a before-insert trigger shouldn't not insert into the same table again - as that would just cause the trigger to fire again, infinitely (until Oracle notices and stops it). You aren't even currently using the v_orta value you're attempting to query.
I suspect you think the trigger is instead of your original insert perhaps, and really you want to set the orta_qiymet value in the newly-inserted row automatically based on the other two columns you have supplied. To do that you don't (and can't) select those values; instead you refer to the :NEW pseudorecord as you are already doing, and then set the third column value in that same pseudorow:
create or replace trigger trig
before insert on sistem
for each row
begin
:new.orta_qiymet := (:new.riyaziyyat + :new.fizika)/2;
end trig;
/
There is a lot of information in the documentation; this is similar to one of the examples.
Related
I have a trigger but it's not inserting the records into target table.
create or replace trigger ins_det_trig1
after insert on Table_a
declare
pragma autonomous_transaction;
---
begin
insert into inf_det
select
a.loc_id,
a.genre_id,
to_char(a.emp_date,'yyyy-mm-dd'),
a.san_seq
from Table_b a ,
Table_a b
where
b.emp_date=a.emp_date
and b.genre_id=a.genre_id
and b.san_seq=a.san_seq;
commit;
exception
when others
Rollback;
end;
pls help me on this
First of all the trigger is invalid, so it won't do anything. You are using a variable named v_err that you don't declare.
Then, you are swallowing all exceptions. If something goes wrong, you fill that variable with the error code and then silently end the trigger. Thus you'll never get informed when the trigger fails.
But the main problem is that you are not using the trigger as you should use triggers in Oracle. The trigger is an after row trigger (AFTER INSERT ... FOR EACH ROW) and hence fires once per row on inserts of table_a rows. The values that got inserted in a new row can be accessed with :new, e.g. :new.business_date.
You, however, ignore these values and select from the table instead. But at the moment of your select the table is mutating. Let's say we write an insert statement that inserts two rows. The trigger fires two times. It is left to chance which row gets inserted first. Oracle sees this and when you are inside the trigger and try to select, it tells us that the content of the table is not deterministic, as the other row may already be in the table or not. We get a mutating table exception.
Having said this: It seems you want an after statement trigger. A trigger that fires after the insert of the rows is complete. For this to happen remove the FOR EACH ROW clause and the related REFERENCING clause, too.
create or replace trigger ins_det_trig1
after insert on Table_a
declare
...
begin
...
end;
I get an error (ORA-04091: table DBPROJEKT_AKTIENDEPOT.AKTIE is mutating, trigger/function may not see it) when executing my trigger:
CREATE OR REPLACE TRIGGER Aktien_Bilanz_Berechnung
AFTER
INSERT OR UPDATE OF TAGESKURS
OR INSERT OR UPDATE OF WERT_BEIM_EINKAUF
ON AKTIE
FOR EACH ROW
DECLARE
bfr number;
Begin
bfr := :new.TAGESKURS - :new.WERT_BEIM_EINKAUF;
UPDATE AKTIE
SET BILANZ = TAGESKURS - WERT_BEIM_EINKAUF;
IF bfr < -50
THEN
DBMS_OUTPUT.PUT_LINE('ACHTUNG: The value (Nr: '||:new.AKTIEN_NR||') is very low!');
END IF;
END;
I want to check the value "BILANZ" after calculating it, wether it is under -50.
Do you have any idea why this error is thrown?
Thanks for any help!
There are several issues here:
Oracle does not allow you to perform a SELECT/INSERT/UPDATE/DELETE against a table within a row trigger defined on that table or any code called from such a trigger, which is why an error occurred at run time. There are ways to work around this - for example, you can read my answers to this question and this question - but in general you will have to avoid accessing the table on which a row trigger is defined from within the trigger.
The calculation which is being performed in this trigger is what is referred to as business logic and should not be performed in a trigger. Putting logic such as this in a trigger, no matter how convenient it may seem to be, will end up being very confusing to anyone who has to maintain this code because the value of BILANZ is changed where someone who is reading the application code's INSERT or UPDATE statement can't see it. This calculation should be performed in the INSERT or UPDATE statement, not in a trigger. It considered good practice to define a procedure to perform INSERT/UPDATE/DELETE operations on a table so that all such calculations can be captured in one place, instead of being spread out throughout your code base.
Within a BEFORE ROW trigger you can modify the values of the fields in the :NEW row variable to change values before they're written to the database. There are times that this is acceptable, such as when setting columns which track when and by whom a row was last changed, but in general it's considered a bad idea.
Best of luck.
You are modifying the table with the trigger. Use a before update trigger:
CREATE OR REPLACE TRIGGER Aktien_Bilanz_Berechnung
BEFORE INSERT OR UPDATE OF TAGESKURS OR INSERT OR UPDATE OF WERT_BEIM_EINKAUF
ON AKTIE
FOR EACH ROW
DECLARE
v_bfr number;
BEGIN
v_bfr := :new.TAGESKURS - :new.WERT_BEIM_EINKAUF;
:new.BILANZ := v_bfr;
IF v_bfr < -50 THEN
Raise_Application_Error(-20456,'ACHTUNG: The value (Nr: '|| :new.AKTIEN_NR || ') is very low!');
END IF;
END;
So I am trying to use triggers to basically set some rules.. If anyone has an ID number lower than 3, he will have to pay only 100 dollars, but if someone has an ID above that, he will have to pay more. I did some research and have been told to use triggers and that triggers are very useful when fetching multiple rows. So I tried doing that but it didn't work. Basically the trigger gets created but then when i try to add values, I get the following error:-
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at "S.PRICTICKET", line 6
ORA-04088: error during execution of trigger 'S.PRICTICKET'
here is what i did to make the trigger:-
CREATE OR REPLACE TRIGGER PRICTICKET BEFORE INSERT OR UPDATE OR DELETE ON PAYS FOR EACH ROW ENABLE
DECLARE
V_PRICE PAYS.PRICE%TYPE;
V_ID PAYS.ID%TYPE;
V_NAME PAYS.NAME%TYPE;
BEGIN
SELECT ID,NAME INTO V_ID,V_NAME FROM PAYS;
IF INSERTING AND V_ID<3 THEN
V_PRICE:=100;
INSERT INTO PAYS(ID,NAME,PRICE) VALUES (V_ID,V_NAME,V_PRICE);
ELSIF INSERTING AND V_ID>=3 THEN
V_PRICE:=130;
INSERT INTO PAYS(ID,NAME,PRICE) VALUES (V_ID,V_NAME,V_PRICE);
END IF;
END;
and the thing is, when i execute this code, i actually do get a message saying the trigger has been compiled. but when when i try to insert values into the table by using the following code, i get the error message I mentioned above.
INSERT INTO PAYS(ID,NAME) VALUES (19,'SS');
You're getting the error you specified, ORA-01422, because you're returning more than one row with the following SELECT:
SELECT ID,NAME INTO V_ID,V_NAME FROM PAYS;
You need to restrict the result set. For example, I'll use the :NEW psuedorecord to grab the row's new ID value, which if unique, will restrict the SELECT to one row:
SELECT ID,NAME INTO V_ID,V_NAME FROM PAYS WHERE ID = :NEW.ID;
Here is the Oracle docs on using triggers: https://docs.oracle.com/database/121/TDDDG/tdddg_triggers.htm#TDDDG99934
However, I believe your trigger has other issues, please see my comments and we can discuss.
EDIT: Based on our discussion.
ORA-04088: error during execution of trigger
Using INSERT inside a BEFORE INSERT trigger on the same table will create an infinite loop. Please consider using an AFTER INSERT and change your INSERTS to UPDATES, or an INSTEAD OF INSERT.
Additionally, remove DELETE from the trigger definition. That makes no sense in this context.
Let's begin clearing up a few things. You were told "triggers are very useful when fetching multiple rows" this is, as a general rule and without additional context, false. There are 4 types of DML triggers:
Before Statement - fires 1 time for the statement regardless of the number of rows processed.
Before Row - fires once for each row processed during the statement before old and new values are merged into a single set of values. At this point you are allowed to change the values in the columns.
After Row - fires once for row processed during the statement after merging old and new values into a single set of values. At this point you cannot change the column values.
After statement - fires once for the statement regardless of the number of rows processed.
Keep in mind that the trigger is effectively part of the statement.
A trigger can be fired for Insert, Update, or Delete. But, there is no need to fire on each. In this case as suggested, remove the Delete. But also the Update as your trigger is not doing anything with it. (NOTE: there are compound triggers, but they contain segments for each of the above).
In general a trigger cannot reference the table that it is fired upon. See error ORA-04091.
If you're firing a trigger on an Insert it cannot do an insert into that same table (also see ORA-04091) and even if you get around that the Insert would fire the trigger, creating a recursive and perhaps a never ending loop - that would happen here.
Use :New.column_name and :Old.column_name as appropriate to refer to column values. Do not attempt to select them.
Since you are attempting to determine the value of a column you must use a Before trigger.
So applying this to your trigger the result becomes:
CREATE OR REPLACE TRIGGER PRICTICKET
BEFORE INSERT ON PAYS
FOR EACH ROW ENABLE
BEGIN
if :new.id is not null
if :new.ID<3 then
:new.Price :=100;
else
:new.Price := 130;
end if ;
else
null; -- what should happen here?
end if ;
END PRICTICKET ;
The below code is giving a mutating error.
Can any1 pls help in solving this.
CREATE OR REPLACE TRIGGER aso_quote_cuhk_trigger
BEFORE INSERT
ON aso.aso_quote_headers_all
FOR EACH ROW
BEGIN
UPDATE aso.aso_quote_headers_all
SET quote_expiration_date=sysdate+90
where quote_header_id=:new.quote_header_id;
END;
/
In oracle there are two levels of triggers: row level and table level.
Row level triggers are executed for each row. Table level triggers executed per statement, even if a statement changed more then one row.
In a row level trigger, you cannot select/update the table itself that has the trigger: you will get a mutating error.
In this case, there is no need for an UPDATE statement. Just try this:
CREATE OR REPLACE TRIGGER aso_quote_cuhk_trigger
BEFORE INSERT
ON aso.aso_quote_headers_all
FOR EACH ROW
BEGIN
:new.quote_expiration_date=sysdate+90;
END;
/
EDIT Rajesh mentioned it is possible, that before inserting a new row, OP wants to update all other records in the aso_quote_headers_all table.
Well, this is feasible, but it's a little tricky. To do this properly, you will need
A pl/sql package and a variable in the package header that is modified by the triggers. This variable could be a list holding the IDs of newly inserted records. Row level after insert trigger would add a new ID to the list. The content of this package variable will be different for each different session, so let's call this variable session_variable.
Row level after insert trigger, that would add new ID to the session_variable.
Table level after insert trigger that would get IDs from the session_variable, process the ID and then remove it from the session_variable. This trigger could execute necessary selects/updates on the aso_quote_headers_all. After a newly inserted ID is processed, this trigger should make sure it gets removed from the session_variable.
I realise you must have resolved your issue by now. However I am adding this answer below to help anyone else facing similar problem as you and I faced.
I recently encountered mutating table (ORA-04091: table XXXX is mutating, trigger/function may not see it) issue and after searching around realised the Compound Triggers feature available in 11g. If you're on 11g following compound trigger would have solved your issue.
CREATE OR REPLACE TRIGGER aso_quote_cuhk_trigger
FOR INSERT ON aso.aso_quote_headers_all
COMPOUND TRIGGER
row_id rowid;
AFTER EACH ROW IS
BEGIN
row_id := :new.rowid;
END AFTER EACH ROW;
AFTER STATEMENT IS
BEGIN
UPDATE aso.aso_quote_headers_all
SET quote_expiration_date = sysdate+90
WHERE rowid = row_id;
END AFTER STATEMENT;
END aso_quote_cuhk_trigger;
/
A word about how it works. This compound trigger fires 2 events :
First is AFTER EACH ROW where we capture the rowid of newly inserted row
Next is AFTER STATEMENT where we update the table using rowid (captured during first event) in the WHERE clause.
A useful link if you want to read more about Compound Triggers.
I have an AFTER INSERT OR UPDATE OR DELETE trigger that I'm writing to store every record revision that occurs in a certain table, by copying the INSERT and UPDATE :NEW values into a mirror table, and for DELETE the :OLD values.
I could un-clutter my code considerably by conditionally passing either the :NEW or :OLD record into a procedure which would then do the insert into my history table. Unfortunately I cannot seem to find a way to pass the entire :OLD or :NEW record.
Am I missing something or is there no way to avoid enumerating every :NEW and :OLD column as I invoke my insert procedure?
I want to do the following:
DECLARE
PROCEDURE LOCAL_INSERT(historyRecord in ACCT.ACCOUNTS%ROWTYPE) IS
BEGIN
INSERT INTO ACCT.ACCOUNTS_HISTORY (ID, NAME, DESCRIPTION, DATE) VALUES (historyRecord.ID, historyRecord.NAME, historyRecord.DESCRIPTION, SYSDATE);
END;
BEGIN
IF INSERTING OR UPDATING THEN
LOCAL_INSERT(:NEW);
ELSE --DELETING
LOCAL_INSERT(:OLD);
END IF;
END;
But I'm stuck doing this:
DECLARE
PROCEDURE LOCAL_INSERT(id in ACCT.ACCOUNTS.ID%TYPE,
name in ACCT.ACCOUNTS.NAME%TYPE,
description in ACCT.ACCOUNTS.DESCRIPTION%TYPE) IS
BEGIN
INSERT INTO ACCT.ACCOUNTS_HISTORY (ID, NAME, DESCRIPTION, DATE) VALUES (id, name, description, SYSDATE);
END;
BEGIN
IF INSERTING OR UPDATING THEN
LOCAL_INSERT(:NEW.ID, :NEW.NAME, :NEW.DESCRIPTION);
ELSE --DELETING
LOCAL_INSERT(:OLD.ID, :OLD.NAME, :OLD.DESCRIPTION);
END IF;
END;
Okay, so it doesn't look like a big difference, but this is just an example with 3 columns rather than dozens.
It isn't. You have to do it yourself through enumeration.
The reasons it can't/doesn't work automatically include:
the :old and :new are default conventions; you can name the :old and :new references to be whatever you want through the REFERENCING clause of the CREATE TRIGGER statement.
you'd have to have a public declaration of a type (through CREATE TYPE or through a package declaration) to be able to use it as an argument to another piece of code.
trigger code is interpreted code, not compiled code.
I don't think it's possible like that. Documentation doesn't mention anything like that.
This would certainly cost performance, but you could try to define your trigger AFTER INSERT and another one BEFORE UPDATE OR DELETE, and in the trigger do something like:
SELECT *
INTO rowtype_variable
FROM accounts
WHERE accounts.id = :NEW.id; -- :OLD.id for UPDATE and DELETE
and then call your procedure with that rowtype_variable.
Use SQL to generate the SQL;
select ' row_field.'||COLUMN_NAME||' := :new.'||COLUMN_NAME||';' from
ALL_TAB_COLUMNS cols
where
cols.TABLE_NAME = 'yourTableName'
order by cols.column_name.
Then copy and paste output.
If you use AFTER trigger you can use rowid as parameter to call procedure
insert into t_hist
select * from t where rowid = r;
If you use BEFORE trigger you will get ORA-04091 mutating table, BUT you solution can be (http://www.dba-oracle.com/t_avoiding_mutating_table_error.htm):
Don't use triggers - The best way to avoid the mutating table error is not to use triggers. While the object-oriented Oracle provides "methods" that are associated with tables, most savvy PL/SQL developers avoid triggers unless absolutely necessary.
Use an "after" or "instead of" trigger - If you must use a trigger, it's best to avoid the mutating table error by using an "after" trigger, to avoid the currency issues associated with a mutating table. For example, using a trigger ":after update on xxx", the original update has completed and the table will not be mutating.
Re-work the trigger syntax - Dr. Hall has some great notes on mutating table errors, and offers other ways to avoid mutating tables with a combination of row-level and statement-level triggers.
Use autonomous transactions - You can avoid the mutating table error by marking your trigger as an autonomous transaction, making it independent from the table that calls the procedure.