I'm having problem with simple trigger command. This trigger operation will insert value into table address_rit when a person who studies at RIT is inserted into table person. Here's the syntax for the trigger command:
CREATE OR REPLACE TRIGGER addr
AFTER INSERT ON person
FOR EACH ROW
WHEN (NEW.college = 'RIT')
BEGIN
INSERT INTO address_rit (name, address, state)
VALUES (NEW.name, NEW.address, (SELECT name FROM states WHERE NEW.statecode = states.statecode));
END;
/
The trigger is compiled but with warning. However, further inspection shows that the trigger actually has error. Here's the error from the compilation.
PL/SQL: SQL Statement ignored ERROR
PL/SQL: ORA-00984: column not allowed here ERROR
I'm pretty sure the error is just a syntax error, but I just can't find any solution. Let me know if I need to add more detail. Thank you very much for your help.
At a minimum, you need a colon before NEW
CREATE OR REPLACE TRIGGER addr
AFTER INSERT ON person
FOR EACH ROW
WHEN (NEW.college = 'RIT')
BEGIN
INSERT INTO address_rit (name, address, state)
VALUES (:NEW.name,
:NEW.address,
(SELECT name
FROM states
WHERE :NEW.statecode = states.statecode));
END;
/
I'm also assuming that the query against the STATES table is always going to return exactly 1 row. If the database is properly normalized, though, I would expect that all the tables would have a STATECODE column rather than a STATE column and that there would be foreign keys between both PERSON and ADDRESS_RIT that reference the STATECODE column in STATES. But, if the database is properly normalized, I would also expect that you wouldn't have an ADDRESS_RIT table that duplicated the data in PERSON. Instead, ADDRESS_RIT really ought to be a view on the PERSON table.
Related
I have this INSERT query, which purpose is to insert the one row in my database.
Similarly I also have a INSERT query which insert multiple rows.
One of the columns in the table is generated after the values has been generated, since it combines a set of column values to construct a name. The name itself it generated from a Trigger, and its triggered After insert, since the column values has to exist for me to generate the name.
my problem now is when I insert one row or multiple rows, I want to know the the generated column value, but when I return it, it states its null?
#$"INSERT INTO registration_table (id, ...,)
VALUES (1,...,)
RETURNING row_id, name;";
which in return gives me an id the one I inserted, but the not actual name but instead I get null..
The trigger is pretty straight forward
CREATE TRIGGER name_insert_trigger
AFTER INSERT
ON registration_table
REFERENCING NEW TABLE AS new_inserts
FOR EACH STATEMENT
WHEN (pg_trigger_depth() = 0)
EXECUTE PROCEDURE registration_entry_name();
CREATE OR REPLACE FUNCTION registration_entry_name()
RETURNS trigger AS
$$
DECLARE
BEGIN
UPDATE registration_table
SET name = |Pattern| -- This one being the actual name generated..
FROM new_inserts
WHERE new_inserts.row_id = registration_table.row_id;
RETURN null;
END;
$$
LANGUAGE plpgsql;
but the insert query above does not return the name?
why not?
You actually need a BEFORE trigger, your data values will be there. The designation of Before and After very often causes misconceptions especially of row level triggers. The terms do not indicate their timing in relation to the DML. I have found it useful to think of them as "before final data values are set" and "after final data values are set" but both run before the invoking DML completes (for now we will bypass deferred triggers). Lets look at inserts. When the before row trigger fires the NEW row contains the values at that point for every column in the row, any value not specified in the statement will be null or contain the specified default if any. Before row triggers can can change any column. After row triggers cannot change columns, if present any change is ignored.
Your description and code imply you need to combine a couple columns to generate the content of another. Since you did not specify exactly that I will build an example and demo.
create table users ( usr_id integer generated always as identity
, lname text not null
, fname text not null
, full_name text not null
) ;
create or replace
function users_bir()
returns trigger
language plpgsql
as $$
begin
if new.full_name is null
then
new.full_name = trim(new.fname) || ' ' || trim(new.lname);
end if;
return new;
end;
$$;
create trigger users_bir_trg
before insert on users
for each row
execute procedure users_bir();
insert into users(fname, lname)
values ( 'George', 'Henery')
, ( 'Samatha', 'van Horm');
insert into users(fname, lname, full_name)
values ( 'Wacky', 'Warriors','Not so tough guys');
This setup allows the full_name to be specified or generated. If only generation is desired remove the IF leaving only the assignment statement. Even better if you have Postgres 12 or higher just define the the column as a generated column. This is also in the demo.
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;
I have written a trigger that does not allow more than two 'Full' ranked professors as part of the faculty (For example, trigger should fire if a new (third) Full professor is added or rank is updated to Full for one of the existing Associate professors.)
It does compile but does not let me know add any data to my table at all. It only needs to be used once. Do I use the statement level trigger for this?
Also, at the moment it does not let me update or insert Professor Rank at all, whether its Full or Associate. How would I fix that?
I have also been told that before/after and that my logic of comparison is wrong. Please help!
Here is the trigger:
CREATE OR REPLACE TRIGGER TRG_PROF_RANK
after insert or update of F_RANK
on FACULTY
DECLARE
FULL_RANK_COUNT integer;
MAX_FULL_RANK_COUNT number :=2;
begin
select count(*) into FULL_RANK_COUNT
from FACULTY
where F_RANK ='Full';
if FULL_RANK_COUNT < MAX_FULL_RANK_COUNT
then
return;
else
if (FULL_RANK_COUNT >= MAX_FULL_RANK_COUNT) then
RAISE_APPLICATION_ERROR (-20000, 'Can only have 2 professors with ranking "Full".');
end if;
end if;
end;
/
I test it with the following statement:
insert into FACULTY values(6, 'John', 'Bonny', 'M', 13, '4079347153', 'Associate', 80000, 2, 6034, Null);
But it doesn't allow me to insert any records into the table. And this is the error that I get:
Error starting at line : 240 in command -
insert into FACULTY values(6, 'John', 'Bonny', 'M', 13, '4079347153', 'Associate', 80000, 2, 6034, Null)
Error report -
SQL Error: ORA-20000: Can only have 2 professors with ranking "Full".
ORA-06512: at "IT337104.TRG_PROF_RANK", line 16
ORA-04088: error during execution of trigger 'IT337104.TRG_PROF_RANK'
20000. 00000 - "%s"
*Cause: The stored procedure 'raise_application_error'
was called which causes this error to be generated.
*Action: Correct the problem as described in the error message or contact
the application administrator or DBA for more information.
please help, I just to make sure I can insert data.
Thank you
The query should raise a mutating table error so the trigger shouldn't be executing at all. You cannot query a table from within a trigger written on that table. You must either maintain the count of full professorships elsewhere or perform the test in your application code before issuing the insert or update. This is a problem with any data integrity check that depends on data in other rows of the same table, other than, of course, a UNIQUE constraint. It simply can't be done from within a trigger on that table.
But even if you could, you have a major logic error. If your table already contains two full professors, this trigger would prevent all Inserts and Updates on the table, even if they did not involve full professors.
But all is not lost. If you fix the logic flaw, turn the trigger into a before trigger for each row, examine the contents of :new.F_RANK and act accordingly, one solution you may want to look into can be found here: Oracle; limit rows per column value. (The second answer with the materialized view, not the first.)
Ok so i am working on a homework assignment.
I have three tables, Movies (title, year, length, genre, studioName, producer) StarsIn (movieTitle, starName) MovieStar (name, address, gender, birthdate)
Basically i need to make sure when someone inserts or updates something in StarsIn those changes need to happen in MovieStar also.
So far i have something like this..
CREATE OR REPLACE TRIGGER testTrig
AFTER UPDATE OR INSERT ON STARSIN
DECLARE
l_name MOVIESTAR.NAME%TYPE;
BEGIN
SELECT NAME FROM MOVIESTAR INTO l_name;
FOR EACH ROW WHEN (new.STARSIN.STARNAME NOT IN l_name)
INSERT INTO MOVIESTAR(NAME) VALUES (new.STARSIN.STARNAME);
END;
I am getting a few compiler errors
Error(4,1): PL/SQL: SQL Statement ignored
Error(4,28): PL/SQL: ORA-00933: SQL command not properly ended
Error(5,10): PLS-00103: Encountered the symbol "ROW" when expecting one of
the following: in
I am very new to oracle and I am practicing Triggers. I know that this could be easily done using foreign keys, but the assignment is to use triggers.
I could really use some help with this. I have tried like a million different ways to make this happen, with no luck.
Thanks in advance for any help/advice.
I'd suggest specifying the trigger fire for each row. I find these a lot easier.
You can do a count to see if the MovieStar.Name value already exists and then insert if it doesn't; that's similar to the approach you have above. This will fail if another user inserts the movie star between the time you check and the time you insert, but it's probably good enough for a class assignment. There are accepted no-fail approaches for this but you may not have covered them in class yet.
Try something like this; it probably incorporates everything you've covered in class so far:
CREATE OR REPLACE TRIGGER TestTrig
AFTER UPDATE OR INSERT ON STARSIN
FOR EACH ROW
DECLARE
movieStarCount NUMBER;
BEGIN
SELECT COUNT(*) INTO movieStarCount
FROM MovieStar
WHERE Name = :NEW.StarName;
IF movieStarCount = 0 THEN
INSERT INTO MovieStar (Name) VALUES (:NEW.StarName);
END IF;
END;
I have the following tables:
FACULTY table
CREATE TABLE "FACULTY"
( "FACULTY_ID" NUMBER(3,0),
"FACULTY_NAME" VARCHAR2(30),
"FACULTY_DEAN" VARCHAR2(30),
CONSTRAINT "FACULTY_PK" PRIMARY KEY ("FACULTY_ID") ENABLE
)
COURSE table
CREATE TABLE "COURSE"
( "COURSE_ID" NUMBER(5,0),
"COURSE_NAME" VARCHAR2(50),
"COURSE_LEVEL" NUMBER,
"FACULTY" NUMBER,
CONSTRAINT "COURSE_PK" PRIMARY KEY ("COURSE_ID") ENABLE
)
so now i want to achieve two things
(1) when a faculty_id is updated on the faculty table. a trigger will fire and update the corresponding rows in the course table with new faculty_id. it will also store the old faculty_id value, name of course, and the date in which the operation is performed in a course_log table.
Below is what I got
create or replace trigger update_faculty
after update on faculty
for each row
begin
insert into course_log
values (:old.faculty_id,
(select course_name
from course
where faculty=:old.faculty_id),
sysdate);
update course
set faculty=:new.faculty_id
where faculty=:old.faculty_id;
end;
But I get the following error.
error ORA-01427: single-row subquery returns more than one row ORA-06512: at "SYSTEM.UPDATE_FACULTY", line 2 ORA-04088: error during execution of trigger 'SYSTEM.UPDATE_FACULTY'
any ideas on how to solve it?
(2) Write a trigger that fires when try change the course_id attribute in the course table, which will check whether the value already exists in the course table and will update successfully if it is a new value. If the value already exists in any row, the trigger will throw an application error saying "The course_id already exists! Update not successful."
below is my query
CREATE OR REPLACE TRIGGER "UPDATE_COURSE_ID"
after update on course
for each row
declare
error number;
begin
select count(*)
into error
from course
where course_id=:new.course_id;
if error > 0 then
raise_application_error (-20000,'The course_id already found! Update not success');
end if;
if error = 0 then
update course set course_id=:new.course_id where course_id=:old.course_id;
end if;
end;
But I got this error
error ORA-04091: table SYSTEM.COURSE is mutating, trigger/function may not see it ORA-06512: at "SYSTEM.UPDATE_COURSE_ID", line 5 ORA-04088: error during execution of trigger 'SYSTEM.UPDATE_COURSE_ID'
For the first question, since you may want to insert multiple rows into the course_log table, you'd need to do something like
create or replace trigger update_faculty
after update on faculty
for each row
begin
-- I'm guessing about the definition of the course_log table
insert into course_log( faculty_id, course_name, log_date )
select :old.faculty_id, course_name, sysdate
from course
where faculty=:old.faculty_id;
update course
set faculty=:new.faculty_id
where faculty=:old.faculty_id;
end;
For the second question, it doesn't make sense to use a trigger. You'd want to use a constraint. And you already have a primary key constraint on course_id in course which is already preventing duplicate course_id values.
Enforcing this sort of thing with triggers is a really poor idea. Since a row level trigger on course cannot query the course table (with the exception of a row-level insert trigger if your insert statements are always of the single-row form INSERT ... VALUES or triggers that use autonomous transactions, neither of which is appropriate here). So if you really wanted to do this with triggers, you'd need to create a package that contained a collection of course_id values, a before statement trigger that initializes the collection, a row-level trigger that adds the :new.course_id to the collection, and an after statement trigger that iterates over the collection and looks for duplicate course_id values. That's a lot of objects to do something that shouldn't be done with triggers in the first place and that is already being done by your constraint. If you're just learning about triggers, I'm guessing that you haven't been taught about packages or collections yet which makes the solution even less appropriate.