I created a trigger to manage the auto_increment but for the reason that I do not know it always shows me this error: maximum number of recursive SQL levels (50) exceeded.
CREATE OR REPLACE TRIGGER auto_increment BEFORE INSERT ON people FOR EACH ROW
DECLARE
mat number;
namm varchar(40);
coun number;
BEGIN
namm:=:new.name;
IF inserting() THEN T
SELECT COUNT(*) INTO coun FROM people;
IF coun = 0 THEN
INSERT INTO people VALUES(100,namm);
ELSE
SELECT MAX(:old.matricule+1) INTO mat FROM people;
INSERT INTO people (matricule,name) VALUES(mat,namm);
END IF;
END IF;
END;
It is recursive because every time a record is inserted into PEOPLE your trigger inserts another record into PEOPLE, which causes the trigger to fire and insert yet another record into PEOPLE, which... well you get the idea.
In an Oracle trigger you just set the :NEW values to change what is being inserted e.g.:
:NEW.matricule := 100;
However, your trigger still would not work because it selects from the same table, which will cause the "table is mutating" exception.
Really the best answer here is to use a sequence - they are designed to avoid these issues as well as giving the best performance. But if you really need this increment functionality, do it before inserting not in a trigger.
Related
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'm trying to use JDBC to access my Oracle DB, and I found out that, for the functions in JDBC to return results correctly, I need to make an iterator for my tables. So, after searching around and figuring out what that means, I came up with the following code snippet to get that done:
--create a sequence for use in the trigger
CREATE SEQUENCE accounts_seq;
--make the trigger on insert or update
CREATE OR REPLACE TRIGGER account_pk_trig
BEFORE INSERT OR UPDATE ON accounts
FOR EACH ROW
BEGIN
IF inserting THEN
SELECT : accounts_seq.NEXTVAL INTO : NEW.accountnumber FROM dual;
ELSE IF updating THEN
SELECT : OLD.accountnumber INTO : NEW.accountnumber FROM dual;
END IF;
END IF;
END;
/
And, not only is Oracle SQL Developer putting the dreaded red underline of doom in the space after the semicolon put after end, but also on the forward slash to end the code block. As far as I've seen, this appears to be correct to the Oracle SQL examples of trigger definitions that I've seen... and I'm not sure if this is due to the Oracle SQL Developer not recognizing NEXTVAL as a keyword... because it isn't highlighted like the others are.
After some fiddling around, I realized that the "ELSE IF" opened a new IF statement that I didn't close. But, still getting Bad Bind variable error.
For those of you who would want to make sure that the "accountnumber" field exists in the table "accounts", here's my definition for the "accounts" table.
CREATE TABLE accounts (
accountnumber NUMBER NOT NULL,
routingnumber NUMBER NOT NULL,
acctype VARCHAR2(20),
balance NUMBER (*,2),
ownerid NUMBER,
CONSTRAINT accountnumber_pk PRIMARY KEY (accountnumber)
);
You have two major errors in your PL/SQL code:
First the select : is wrong. You can't just throw in a colon like that. The NEW and OLD records do need a colon, but without a space. :new, not : new.
To store the result of a query in a variable you need:
select accounts_seq.NEXTVAL
INTO :NEW.accountnumber
FROM dual;
But you don't need a SELECT for that, you can use a simple variable assignment:
:NEW.accountnumber := accounts_seq.NEXTVAL;
You also have two END IFs although you only have a single IF
And as documented in the manual it needs to be ELSIF, not ELSE IF
Putting all that together, your trigger should be:
CREATE OR REPLACE TRIGGER account_pk_trig
BEFORE INSERT OR UPDATE ON accounts
FOR EACH ROW
BEGIN
IF inserting THEN
:NEW.accountnumber := accounts_seq.NEXTVAL;
ELSIF updating THEN
:NEW.accountnumber := :OLD.accountnumber;
END IF;
END;
/
As the trigger is declared as BEFORE INSERT OR UPDATE the ELSIF is actually useless, because it can only be insert or updating nothing else. So instead of ELSIF updating THEN you could simply write ELSE
This might appear a simple query for most of you, but I am a beginner in Oracle DB.
A table has been created with below script-
CREATE TABLE PLAN_TABLE
(
PL_ID DECIMAL(10,0) PRIMARY KEY NOT NULL
,PL_NAME VARCHAR2(300) DEFAULT NULL
,UPDATED_TS TIMESTAMP DEFAULT SYSDATE NOT NULL
,DELETE_FLAG DECIMAL(10,0) DEFAULT 0 NOT NULL
);
The requirement is to have SYSDATE for UPDATED_TS for any new record inserted into the table and also in case when the DELETE_FLAG is updated to 1. Can it be done by trigger?
The below trigger was created-
CREATE OR REPLACE TRIGGER PT_BEFORE_INSERT_TR
BEFORE INSERT ON PLAN_TABLE
FOR EACH ROW
BEGIN
SELECT SYSDATE INTO :new.UPDATED_TS FROM DUAL;
dbms_output.put_line('Inserted');
END;
/
Below error was encountered while inserting record into the table-
error: ORA-04091: table I60_SCH04.PLAN_TABLE is mutating, trigger/function may not see it
Can you please help in letting me know that where am I committing the mistake? Is there any better way to achieve the requirement based upon INSERT/UPDATE?
The actual error you get is due to the fact that you try to select from a table that you actually are changing. To prevent the issue there are a couple of methods, but in you case things are really simple.
SYSDATE is a function, that you could call directly inside PL/SQL block (which a trigger actually is) and use the value returned to update the set the column value
CREATE OR REPLACE TRIGGER PT_BEFORE_INSERT_TR
BEFORE INSERT ON PLAN_TABLE
FOR EACH ROW
BEGIN
:new.UPDATED_TS := sysdate;
dbms_output.put_line('Inserted');
END;
/
OK, this covers the insert part.
For updating - once again, many options. One could be - change your trigger to BEFORE INSERT OR UPDATE ON PLAN_TABLE.
In this case whenever you issue update or insert - this trigger is fired for each row and updates the date column accordingly.
And of course you could use particular checks available in triggers, something like
IF INSERTING OR UPDATING('DELETE_FLAG') THEN
...
END IF;
and code in the logic you need.
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.
I recently started working on a large complex application, and I've just been assigned a bug due to this error:
ORA-04091: table SCMA.TBL1 is mutating, trigger/function may not see it
ORA-06512: at "SCMA.TRG_T1_TBL1_COL1", line 4
ORA-04088: error during execution of trigger 'SCMA.TRG_T1_TBL1_COL1'
The trigger in question looks like
create or replace TRIGGER TRG_T1_TBL1_COL1
BEFORE INSERT OR UPDATE OF t1_appnt_evnt_id ON TBL1
FOR EACH ROW
WHEN (NEW.t1_prnt_t1_pk is not null)
DECLARE
v_reassign_count number(20);
BEGIN
select count(t1_pk) INTO v_reassign_count from TBL1
where t1_appnt_evnt_id=:new.t1_appnt_evnt_id and t1_prnt_t1_pk is not null;
IF (v_reassign_count > 0) THEN
RAISE_APPLICATION_ERROR(-20013, 'Multiple reassignments not allowed');
END IF;
END;
The table has a primary key "t1_pk", an "appointment event id"
t1_appnt_evnt_id and another column "t1_prnt_t1_pk" which may or may
not contain another row's t1_pk.
It appears the trigger is trying to make sure that nobody else with the
same t1_appnt_evnt_id has referred to the same one this row is referring to a referral to another row, if this one is referring to another row.
The comment on the bug report from the DBA says "remove the trigger, and perform the check in the code", but unfortunately they have a proprietary code generation framework layered on top of Hibernate, so I can't even figure out where it actually gets written out, so I'm hoping that there is a way to make this trigger work. Is there?
I think I disagree with your description of what the trigger is trying to
do. It looks to me like it is meant to enforce this business rule: For a
given value of t1_appnt_event, only one row can have a non-NULL value of
t1_prnt_t1_pk at a time. (It doesn't matter if they have the same value in the second column or not.)
Interestingly, it is defined for UPDATE OF t1_appnt_event but not for the other column, so I think someone could break the rule by updating the second column, unless there is a separate trigger for that column.
There might be a way you could create a function-based index that enforces this rule so you can get rid of the trigger entirely. I came up with one way but it requires some assumptions:
The table has a numeric primary key
The primary key and the t1_prnt_t1_pk are both always positive numbers
If these assumptions are true, you could create a function like this:
dev> create or replace function f( a number, b number ) return number deterministic as
2 begin
3 if a is null then return 0-b; else return a; end if;
4 end;
and an index like this:
CREATE UNIQUE INDEX my_index ON my_table
( t1_appnt_event, f( t1_prnt_t1_pk, primary_key_column) );
So rows where the PMNT column is NULL would appear in the index with the inverse of the primary key as the second value, so they would never conflict with each other. Rows where it is not NULL would use the actual (positive) value of the column. The only way you could get a constraint violation would be if two rows had the same non-NULL values in both columns.
This is perhaps overly "clever", but it might help you get around your problem.
Update from Paul Tomblin: I went with the update to the original idea that igor put in the comments:
CREATE UNIQUE INDEX cappec_ccip_uniq_idx
ON tbl1 (t1_appnt_event,
CASE WHEN t1_prnt_t1_pk IS NOT NULL THEN 1 ELSE t1_pk END);
I agree with Dave that the desired result probalby can and should be achieved using built-in constraints such as unique indexes (or unique constraints).
If you really need to get around the mutating table error, the usual way to do it is to create a package which contains a package-scoped variable that is a table of something that can be used to identify the changed rows (I think ROWID is possible, otherwise you have to use the PK, I don't use Oracle currently so I can't test it). The FOR EACH ROW trigger then fills in this variable with all rows that are modified by the statement, and then there is an AFTER each statement trigger that reads the rows and validate them.
Something like (syntax is probably wrong, I haven't worked with Oracle for a few years)
CREATE OR REPLACE PACKAGE trigger_pkg;
PROCEDURE before_stmt_trigger;
PROCEDURE for_each_row_trigger(row IN ROWID);
PROCEDURE after_stmt_trigger;
END trigger_pkg;
CREATE OR REPLACE PACKAGE BODY trigger_pkg AS
TYPE rowid_tbl IS TABLE OF(ROWID);
modified_rows rowid_tbl;
PROCEDURE before_stmt_trigger IS
BEGIN
modified_rows := rowid_tbl();
END before_each_stmt_trigger;
PROCEDURE for_each_row_trigger(row IN ROWID) IS
BEGIN
modified_rows(modified_rows.COUNT) = row;
END for_each_row_trigger;
PROCEDURE after_stmt_trigger IS
BEGIN
FOR i IN 1 .. modified_rows.COUNT LOOP
SELECT ... INTO ... FROM the_table WHERE rowid = modified_rows(i);
-- do whatever you want to
END LOOP;
END after_each_stmt_trigger;
END trigger_pkg;
CREATE OR REPLACE TRIGGER before_stmt_trigger BEFORE INSERT OR UPDATE ON mytable AS
BEGIN
trigger_pkg.before_stmt_trigger;
END;
CREATE OR REPLACE TRIGGER after_stmt_trigger AFTER INSERT OR UPDATE ON mytable AS
BEGIN
trigger_pkg.after_stmt_trigger;
END;
CREATE OR REPLACE TRIGGER for_each_row_trigger
BEFORE INSERT OR UPDATE ON mytable
WHEN (new.mycolumn IS NOT NULL) AS
BEGIN
trigger_pkg.for_each_row_trigger(:new.rowid);
END;
With any trigger-based (or application code-based) solution you need to
put in locking to prevent data corruption in a multi-user environment.
Even if your trigger worked, or was re-written to avoid the mutating table
issue, it would not prevent 2 users from simultaneously updating
t1_appnt_evnt_id to the same value on rows where t1_appnt_evnt_id is not
null: assume there are currenly no rows where t1_appnt_evnt_id=123 and
t1_prnt_t1_pk is not null:
Session 1> update tbl1
set t1_appnt_evnt_id=123
where t1_prnt_t1_pk =456;
/* OK, trigger sees count of 0 */
Session 2> update tbl1
set t1_appnt_evnt_id=123
where t1_prnt_t1_pk =789;
/* OK, trigger sees count of 0 because
session 1 hasn't committed yet */
Session 1> commit;
Session 2> commit;
You now have a corrupted database!
The way to avoid this (in trigger or application code) would be to lock
the parent row in the table referenced by t1_appnt_evnt_id=123 before performing the check:
select appe_id
into v_app_id
from parent_table
where appe_id = :new.t1_appnt_evnt_id
for update;
Now session 2's trigger must wait for session 1 to commit or rollback before it performs the check.
It would be much simpler and safer to implement Dave Costa's index!
Finally, I'm glad no one has suggested adding PRAGMA AUTONOMOUS_TRANSACTION to your trigger: this is often suggested on forums and works in as much as the mutating table issue goes away - but it makes the data integrity problem even worse! So just don't...
I had similar error with Hibernate. And flushing session by using
getHibernateTemplate().saveOrUpdate(o);
getHibernateTemplate().flush();
solved this problem for me. (I'm not posting my code block as I was sure that everything was written properly and should work - but it did not until I added the previous flush() statement). Maybe this can help someone.