Good day everyone,
I'm having trouble making my trigger work. As far as the functionality of the body and how it behaves, it does exactly as I intended for it to behave. However, when I start to fire the trigger, it returns an error in which Triggers should not have a SELECT statement from inside the main body. I'm still fairly new to coding and how to materialize the idea in my head into code. Hopefully someone could point me in a right direction on how change the Trigger I would like to have as a final result. Please see below script.
Update: Expected result would be whenever a user UPDATE a row and INSERT a new record via the application or job being run in the background, S1_HOVER_REPORT column would be updated with the value from the SELECT script and use the data from the S1_HOVER case result.
(Edit: I have updated the details of the problem above, added the Table being used and Error return)
Table: SITE
Column Name Type
------------------------------
ID VARCHAR2(14)
NAME VARCHAR2(70)
TYPE_CODE VARCHAR2(2)
PARENT VARCHAR2(14)
S1_HOVER_REPORT VARCHAR2(14)
CREATE OR REPLACE TRIGGER MESS.S1_HOVER_REPORT
AFTER INSERT OR UPDATE ON MESS.SITE
FOR EACH ROW
BEGIN
UPDATE (SELECT S1.ID,
S1.NAME,
S1.TYPE_CODE,
S1.PARENT AS PARENT1,
S2.PARENT AS PARENT2,
S1.S1_HOVER_REPORT,
CASE
WHEN (S1.TYPE_CODE = 'H2') THEN S1.PARENT
WHEN (S1.TYPE_CODE = 'S1') THEN S2.PARENT
ELSE S1.ID
END AS S1_HOVER
FROM SITE S1,
(SELECT ID,
NAME,
PARENT,
TYPE_CODE
FROM site
WHERE type_code='H2') S2
WHERE S1.PARENT=S2.ID
OR S1.ID = S2.PARENT) S3
SET S3.S1_HOVER_REPORT = S3.S1_HOVER;
END;
Error returned when Trigger fired:
Error report -
SQL Error: ORA-01779: cannot modify a column which maps to a non key-preserved table
ORA-06512: at "MES.S1_HOVER_REPORT", line 2
ORA-04088: error during execution of trigger 'MES.S1_HOVER_REPORT'
01779. 00000 - "cannot modify a column which maps to a non key-preserved table"
*Cause: An attempt was made to insert or update columns of a join view which
map to a non-key-preserved table.
*Action: Modify the underlying base tables directly.
(Update: I have included the updated trigger and it's now compiling without any issue, but I'm having errors whenever I try updating a record)
CREATE OR REPLACE TRIGGER MESS.S1_HOVER_REPORT
BEFORE INSERT OR UPDATE ON MESS.SITE
FOR EACH ROW
DECLARE
v_S1_HOVER_REPORT VARCHAR2(14);
BEGIN
SELECT CASE
WHEN (S1.TYPE_CODE = 'H2') THEN S1.PARENT
WHEN (S1.TYPE_CODE = 'S1') THEN S2.PARENT
ELSE (S1.ID)
END AS S1_HOVER
INTO v_S1_HOVER_REPORT
FROM SITE S1,
(SELECT ID,
NAME,
PARENT,
TYPE_CODE
FROM site
WHERE type_code='H2') S2
WHERE S1.PARENT=S2.ID
OR S1.ID = S2.PARENT;
:NEW.S1_HOVER_REPORT := v_S1_HOVER_REPORT;
END;
Error report -
SQL Error: ORA-04091: table MES.SITE is mutating, trigger/function may not see it
ORA-06512: at "MES.S1_HOVER_REPORT", line 4
ORA-04088: error during execution of trigger 'MES.S1_HOVER_REPORT'
04091. 00000 - "table %s.%s is mutating, trigger/function may not see it"
*Cause: A trigger (or a user defined plsql function that is referenced in
this statement) attempted to look at (or modify) a table that was
in the middle of being modified by the statement which fired it.
*Action: Rewrite the trigger (or function) so it does not read that table.
Firstly from the error message
An attempt was made to insert or update columns of a join view which map to a non-key-preserved table.
S3 is the veiw ( you are creating the view by doing a select inside an update statment). You can try and change this to have key preservation but I really wouldn't know how.
The error suggests updating the base tables not the view. So as mentioned in the comments :old and :new are your friend.
:OLD holds all the values of the table the trigger is created on BEFORE the update (null if insert)
:NEW holds all the values of the table the trigger is created on AFTER the update / insert.....
So if I understand what you want to do correctly you would need to...
declare a variable eg v_S1_hover_report
do your select returning whatever value you need into this variable
set the value in your site table by doing
:NEW.S1_HOVER_REPORT := v_S1_hover_report
By setting this value into the :NEW object when a commit happens it will be committed to the database. This completely removes the need for an update statement in the trigger.
You can also use :NEW.id in your select statement to filter it down to the record you are updating if it is helpfull
CREATE OR REPLACE TRIGGER MESS.S1_HOVER_REPORT
AFTER INSERT OR UPDATE ON MESS.SITE
FOR EACH ROW
v_test varchar2(10);
BEGIN
select 'Your value' into v_test from dual;
:new.s1_hover_report := v_test;
END;
OR
CREATE OR REPLACE TRIGGER MESS.S1_HOVER_REPORT
AFTER INSERT OR UPDATE ON MESS.SITE
FOR EACH ROW
v_test varchar2(10);
BEGIN
select 'Your value' into :new.s1_hover_report from dual;
END;
Related
I'm taking my first steps in Pl/SQL and am struggling with triggers. I've tried creating the trigger below but am receiving this error:
Error at line 2: PL/SQL: SQL Statement ignored
PL/SQL: ORA-00942: table or view does not exist
To clarify: I have checked the name of the table over and over, and it does exist. It is also in the same schema as the trigger I'm trying to create. The 'customer_seq.NEXTVAL' refers to a sequence created previously that runs without errors.
The code is as follows:
CREATE TRIGGER new_customer
BEFORE INSERT ON customer
FOR EACH ROW
BEGIN
INSERT INTO customer_id VALUES ('c-', customer_seq.NEXTVAL);
END;
Thanks in advance for any help.
You probably intend something like this:
CREATE TRIGGER new_customer
BEFORE INSERT ON customer
FOR EACH ROW
BEGIN
SELECT customer_seq.NEXTVAL INTO :NEW.customer_id
FROM dual;
END;
It is unclear what the purpose of 'C_' is. If it is part of the customer id, I would advise you to stick to numbers.
Also note that more recent versions of Oracle support generated always as identity -- which is much preferred over defining a sequence and trigger.
this is my trigger :
create trigger tampone_trigger
after insert on tamponi.numerotelpaziente
for each row
begin
IF ( :new.numerotelpaziente not in (
select numtel
from users))
then
insert into spaiati values (new.numtel);
end if;
end;
The table "Tamponi" does exists, and "numerotelpaziente" is one of the columns...
Table "USERS" also exists, and "numtel" is one of its columns...
Why on earth is giving me that one error?
The trigger is supposed to look for this new cellPhone number inserted into "Tamponi" and check if this number exists in "Users", if not it has to be add to the separated table "spaiati" , where there is a column for it..
It is perfectly connected to my personal database (i'm running my JAVAfx application onto it, and it works fine, i just need to create some triggers).
Report error -
ORA-00942: table or view does not exist
00942. 00000 - "table or view does not exist"
*Cause:
*Action:
If i use "on Tamponi" instead of giving the column aswell, the error becomes this one :
Report error -
ORA-04082: NEW or OLD references not allowed in table level triggers
04082. 00000 - "NEW or OLD references not allowed in table level triggers"
*Cause: The trigger is accessing "new" or "old" values in a table trigger.
*Action: Remove any new or old references.
if i use "on tamponi" the error is now this :
2/5 PL/SQL: Statement ignored
2/40 PLS-00405: subquery not allowed in this context
Errori: controllare il log del compilatore
Since this code will be in a trigger, you will want it to be as efficient as possible since it might be run very often. The code below should do what you are hoping to achieve with minimal context switching.
CREATE TRIGGER tampone_trigger
AFTER INSERT
ON tamponi
FOR EACH ROW
BEGIN
INSERT INTO spaiati
SELECT :new.numerotelpaziente
FROM DUAL
WHERE NOT EXISTS
(SELECT 1
FROM users u
WHERE u.numtel = :new.numerotelpaziente);
END;
/
You can try this -
create trigger tampone_trigger
after insert on tamponi
for each row
declare
v_flag boolean := false;
begin
for c in (select numtel from users)
loop
if :new.numerotelpaziente = c.numtel
then
v_flag := true;
exit;
end if;
exit when no_data_found;
end loop;
insert into spaiati values (new.numtel);
end;
I don't have a DB client available currently, but this should be close to what you want:
create trigger tampone_trigger
after insert on tamponi for each row
declare
v_exists number;
begin
select count(*) into v_exists from users u where u.numtel = :new.numerotelpaziente;
if (v_exists = 0) then
insert into spaiati values(:new:numerotelpaziente);
end if;
end;
I have a trigger set to fire after an update of a specific column. I want to update the value of a specific column after a specific value from another column changes to another specific value.
I'm getting the errors:
ORA-04091: table tableName is mutating, trigger/function may not see it
ORA-06512: at "triggerName", line 14
ORA-04088: error during execution of trigger 'triggerName'
I've rewritten this as a before update and after update, as well as tried storing the logic in a function, and using "pragma autonomous_transaction", but the error still gets thrown.
BEFORE update of columnName1 ON tableName
FOR EACH ROW
BEGIN
if :new.columnName1 = 3 AND :old.columnName1 = 1 then
update tablename
set columnName2= MOD(sequenceName.NextVal, 5) + 1
where tableName.columnName2 = :old.columnName2;
end if;
END;
/
I don't understand why the entire table is labelled as "mutating" when I am not updating the column affected by the update the trigger is responding to. Surely, you should be able to update the value of a column in a table if another value in the table changes, or am I crazy here?
Note: Only one entry would be affected at a time. In my application logic, I update the status of some person in the database. I want the database to do some logic only on a specific status change, and I want to avoid using API calls for the logic here, as you can see, it is simply one line of logic in PLSQL.
Thanks
Perhaps you don't really want to update the table but just change a value in the specific row being updated.
If so, eschew the update and just set the value:
BEFORE update of columnName1 ON tableName
FOR EACH ROW
BEGIN
if :new.columnName1 = 3 AND :old.columnName1 = 1 then
:new.columnName2 := MOD(sequenceName.NextVal, 5) + 1 ;
end if;
END;
I am new to PLSQL in Oracle. When I am learning about triggers, I have read from this source https://www.techonthenet.com/oracle/triggers/before_insert.php which says that when I create a BEFORE INSERT Trigger in Oracle, the FOR EACH ROW is NOT always needed, hence the syntax is enclosed by square brackets [ ]. I have written this simple trigger:
CREATE OR REPLACE TRIGGER enroll_time
BEFORE INSERT
ON ENROLL
FOR EACH ROW
BEGIN
:new.addtime := sysdate;
END;
/
If I remove the FOR EACH ROW in the above, I actually get an error:
Error report -
ORA-04082: NEW or OLD references not allowed in table level triggers
04082. 00000 - "NEW or OLD references not allowed in table level triggers"
*Cause: The trigger is accessing "new" or "old" values in a table trigger.
*Action: Remove any new or old references.
From the error message, it seems like if I use :new.[column_name], then FOR EACH ROW must have to exist. Why is this? Is there any example that FOR EACH ROW is NOT needed in a BEFORE INSERT TRIGGER in Oracle?
Is there any example that FOR EACH ROW is NOT needed in a BEFORE INSERT TRIGGER in Oracle?
Simple example of statement level trigger:
CREATE TABLE test_table(col VARCHAR2(10));
CREATE OR REPLACE TRIGGER enroll_time
BEFORE INSERT
ON ENROLL
BEGIN
INSERT INTO test_table(col)
SELECT 1 FROM dual;
END;
/
I highly recommend to read about compound trigger to understand when each part is fired.
Basically, if you need to use :OLD or :NEW pseudotables, you need a row level trigger. An example of a statement level trigger would be inserting a record into a table when another table is effected.
I'm creating a row-level trigger for Oracle using SQL Tools. I will attach a picture of the ERD I am working off of. I will also include my instructions, paste what code I have tried, and the error I am getting.
Description of request:
Create a row-level trigger named "TRG_USED_COST" on the USED table. The trigger should execute BEFORE a new row is inserted in the table. The insert command will provide a value for "CHEM_NUM","JOB_NUM", and "USED_QTY" that are being added to the table. Using the CHEM_NUM being used in the insert, retrieve the "CHEM_UNIT_COST" from the CHEMICAL table. Multiply the chemical unit cost times the quantity of chemicals used in this row, and include that value as the "USED_CHARGE" for the row being inserted.
My code:
CREATE OR REPLACE TRIGGER TRG_USED_COST
BEFORE INSERT OR UPDATE OF CHEM_NUM,JOB_NUM,USED_QTY ON USED
FOR EACH ROW
BEGIN
UPDATE USED
SET USED_CHARGE = CHEM_UNIT_COST * USED_QTY
WHERE CHEM_NUM IS NOT NULL;
END;
/
After I enter the code, I receive the error:
PL/SQL: ORA-00904: "CHEM_UNIT_COST": invalid identifier
I know that I'm getting the error because I did not reference the CHEMICAL table that "CHEM_UNIT_COST" is located in...but I don't know how to reference it.
You have several issues here. First, you do not "update" the target table in this case. Use the :new attribute on the trigger. Then select the cost from the other table.
CREATE OR REPLACE TRIGGER TRG_USED_COST
BEFORE INSERT OR UPDATE OF CHEM_NUM,JOB_NUM,USED_QTY ON USED
FOR EACH ROW
DECLARE
v_cost CHEMICAL.CHEM_UNIT_COST%TYPE;
BEGIN
SELECT CHEM_UNIT_COST
INTO v_cost
FROM CHEMICAL
WHERE CHEM_NUM = :new.CHEM_NUM;
:new.USED_CHARGE := v_cost * :new.USED_QTY;
END;
/