Hey I wanted to create a function that adds absences to the student if he has 3 absence in one material that mean his eliminated I wanted to create a function that adds absent and he reached 3 absences that mean his eliminated but the problem that when I try the function it doesn't add to the previous table but it create another row
CREATE TABLE abssance (
id_abssance SERIAL PRIMARY KEY,
id_etudiant int,
id_matiere int,
abss int,
eliminé int
);
create or replace function test2(etudiant int, matiere int, abssancee int)
RETURNs int as
$$
begin
update abssance set id_etudiant=etudiant,id_matiere=matiere, abss= abssancee + 1 where abss > 2;
if abssancee=3
then
update abssance set eliminé=1 ;
return 1;
else
return 0;
end if;
end $$
language plpgsql;
Always returns 0 doesn't add another value in the actual row that I wanna updated it
resault that i get is this
But I wanted it like this
and if the abss= 3 it will add 1 on the eliminé
The where clause of the update sounds wrong. Logically, you don't want to update ALL rows having 2 absences, but rather to update ONE row for the given student/course
update abssance
set abss= abssancee + 1
WHERE id_etudiant=etudiant AND id_matiere=matiere;
Similarly, the update for elimine is missing the where clause to update the proper student
update abssance
set eliminé=1
WHERE id_etudiant=etudiant;
Related
I'm trying to make a trigger to avoid inserting data in the table for this reason:
If a patient is dead he can't make a visit.
I made a function that return a 1 if the patient is dead and I call it on the trigger. That's the code:
CREATE OR REPLACE FUNCTION check_d (pd INTEGER)
RETURN INTEGER
IS
d Patient.d_date%TYPE;
BEGIN
SELECT P.d_Date INTO d
FROM Patient P
WHERE P.idP=pd;
IF d <> NULL THEN
RETURN 1;
ELSE
RETURN 0;
END IF;
END;
CREATE OR REPLACE TRIGGER bad_insert
BEFORE INSERT ON Visit
FOR EACH ROW
DECLARE
idd INTEGER;
dp Visit.id_PV%TYPE;
BEGIN
SELECT V.id_PV INTO dp
FROM Visit V
WHERE id_PV=:NEW.id_PV;
idd := check_d(dp);
IF idd = 1 THEN
RAISE_APPLICATION_ERROR(-20014,'Error. Patient Deceased.');
END IF;
END;
/
The function should be ok, the problem is in thet trigger.
Visit.id_PV is a Foreign Key to Patient.idP(PRIMARY KEY) anyway. How should I modify the code? Thanks.
Your function is not correct
d <> NULL
Will always return UNKNOWN, instead you have to check for nulls like:
d is not null
Once you've fixed that, you still have to work around the mutating table error you'd receive when you try an insert statement (did you not receive this when you tried it?). You are referencing the same table you are inserting into within your trigger. You can't do that. Instead you should reference the column you want using :new.id_PV .
I think the problem is located here :
IF d <> NULL THEN
Change it to :
IF d IS NOT NULL THEN
In the current case, you'll get no_data_found exception because of the query within the trigger. Moreover, you do not need to return the value for id_PV column that you already have as :NEW.id_PV, and such attempt mostly end with mutating trigger error. So , rearrange your trigger as
CREATE OR REPLACE TRIGGER bad_insert
BEFORE INSERT ON Visit
FOR EACH ROW
BEGIN
IF check_d(:NEW.id_PV) = 1 THEN
RAISE_APPLICATION_ERROR(-20014, 'Error. Patient Deceased.');
END IF;
END;
/
while getting rid of redundant local variables.
The function might also be made brief such as
CREATE OR REPLACE FUNCTION check_d (pd Visit.id_PV%type) RETURN INT IS
val INT;
BEGIN
SELECT NVL(SUM(NVL2(P.d_Date,1,0)),0)
INTO val
FROM Patient P
WHERE P.idP=pd;
RETURN val;
END;
/
Demo
This MWE is NOT how you would typically solve this problem, however, it is as simple as I can explain the problem I am encountering. I am merely trying to point out 2 things
I am doing more than simply returning the contents of a Table
What is being returned is NOT being returned as a Table but a String
Supporting SQL Statements:
DROP DATABASE IF EXISTS test;
CREATE DATABASE test;
\c test
CREATE TABLE credit_card(
id BIGSERIAL PRIMARY KEY,
balance BIGINT
);
Functions:
CREATE FUNCTION get_credit_card(
p_id BIGINT
)
RETURNS TABLE(
id BIGINT,
balance BIGINT
)
AS $$
DECLARE
BEGIN
RETURN QUERY
SELECT
credit_card.id,
credit_card.balance
FROM
credit_card
WHERE
credit_card.id = p_id;
END $$ LAnguage 'plpgsql';
CREATE FUNCTION pay_with_card(
p_id BIGINT,
p_amount BIGINT
)
RETURNS TABLE(
id BIGINT,
balance BIGINT
)
AS $$
DECLARE
v_balance BIGINT;
BEGIN
SELECT
credit_card.balance
FROM
credit_card
INTO
v_balance
WHERE
credit_card.id = p_id;
IF v_balance < p_amount
THEN
RETURN;
END IF;
UPDATE
credit_card
SET
balance = credit_card.balance - p_amount;
RETURN QUERY
SELECT get_credit_card (p_id);
END $$ LAnguage 'plpgsql';
Populate Table and Call function:
INSERT INTO credit_card
(balance)
VALUES
(100);
SELECT
pay_with_card (1, 100);
Error:
DROP DATABASE
CREATE DATABASE
You are now connected to database "test" as user "postgres".
CREATE TABLE
CREATE FUNCTION
CREATE FUNCTION
INSERT 0 1
psql:test.sql:74: ERROR: structure of query does not match function result type
DETAIL: Returned type record does not match expected type bigint in column 1.
CONTEXT: PL/pgSQL function pay_with_card(bigint,bigint) line 24 at RETURN QUERY
It took me a long time to figure out that pay_with_card is returning a String, or what appears to be a String, instead of a TABLE(id BIGINT, balance BIGINT). With the Python psycopg2 library, the returned query is
[('(1,100)'),]
So my entire code is breaking because I can't get the values (unless I hack it and use string manipulation.
Question:
How can I fix it so that it returns the correct query like so
[(1,100),]
An alternative to the hint in horse_with_no_name's comment, you can replace
RETURN QUERY
SELECT get_credit_card (p_id);
with
RETURN QUERY SELECT (get_credit_card(p_id)).*;
You need some way of expanding the returned record back into its constituent fields. (I think horse’s SELECT * … has the same effect.)
I am trying to achieve here is to basically override 0 rows Updated, when UPDATE is issued in-case the actual PK/UK value doesn't exist in the table. This is what I have done:
Actual Table:
CREATE TABLE fdrgiit.vereine(
team numeric(10) primary key,
punkte int not null,
serie int not null
);
Dummy Table:
CREATE TABLE fdrgiit.dummyup
(
id numeric(1) PRIMARY KEY,
datetest timestamp
);
Inserted records in both the tables:
insert into vereine(team,punkte,serie) values(1, 50, 1);
insert into vereine(team,punkte,serie) values(2, 30, 1);
insert into vereine(team,punkte,serie) values(3, 25, 1);
insert into vereine(team,punkte,serie) values(4, 37, 2);
insert into dummyup values(1, now());
Created the following function and trigger:
create or replace function updateover()
returns trigger as
$BODY$
begin
if EXISTS (select 1 FROM vereine WHERE team = new.team ) then
RETURN NEW;
else
UPDATE fdrgiit.dummyup set datetest=now() where id=1;
RETURN NULL;
end if;
end;
$BODY$
LANGUAGE plpgsql;
create trigger update_redundancy
before update on vereine
for each row
execute procedure updateover() ;
But when I execute an UPDATE like this on the , I am still get 0 rows affected
update vereine set punkte=87 where team=5;
Kindly review and please suggest if this is something that can be done.
You cannot trigger anything with an UPDATE that does not affect row as triggers are only fired for affected rows.
But you could wrap your alternative UPDATE into a function:
CREATE OR REPLACE FUNCTION updateover()
RETURNS int AS
$func$
UPDATE dummyup
SET datetest = now()
WHERE id = 1
RETURNING 2;
$func$ LANGUAGE sql;
... and run your UPDATE nested like this:
WITH upd AS (
UPDATE vereine
SET punkte = 87
WHERE team = 5 -- does not exist!
RETURNING 1
)
SELECT 1 FROM upd
UNION ALL
SELECT updateover()
LIMIT 1;
db<>fiddle here
If no row qualifies for an UPDATE, then 1st outer SELECT 1 FROM upd returns no row and Postgres keeps processing the 2nd SELECT updateover(). But if at least one row is affected, the final SELECT is never executed. Exactly what you want.
This updates dummyup one time if the UPDATE on vereine does not affect any rows; never several times. But that's ok, since now() is STABLE for the duration of the transaction.
Related:
Return a value if no record is found
I'm new to SQL and I'm trying to update a column (ex_counter) of a table (ex_table). This column consists of a counter of the number of times an ID (ex_id) appears on a second table (ex2_id in ex2_table).
An ID can be inserted into the second table at any moment. If that ID is already existing, the counter of its corresponding ID in the first table must be updated (by simply adding 1, I guess).
These are the two tables:
CREATE TABLE ex_table(
ex_id SMALLINT,
ex_counter SMALLINT;)
CREATE TABLE ex2_table(
ex2_id SMALLINT;)
I think it should be done more or less like this. The commented code is the pseudocode that I don't know how to implement:
CREATE TRIGGER ex_trigger AFTER
INSERT ON ex2_table
FOR EACH ROW EXECUTE PROCEDURE ex_func();
CREATE FUNCTION ex_func() RETURNS trigger AS $$ BEGIN
/*
if ex2_id = ex_id
ex_counter = ex_counter + 1
*/
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
Thanks in advance!
Something like this
IF EXISTS (SELECT * FROM ex_table WHERE ex_id = new.ex2_id) THEN
UPDATE ex_table
SET ex_counter = ex_counter + 1
WHERE ex_id = new.ex2_id
ELSE
INSERT INTO ex_table VALUES (new.ex2_id, 1)
END IF;
Note that it is no point really to store a counter since you so easily can retrieve the value by doing a SELECT COUNT()...
I am trying to create a trigger, so that when ever I add a new record it adds another record in the same table. The session field will only take values between 1 and 4. So when I add a 1 in session I want it to add another record but with session 3 blocked. But the problem is that it leads to cascading triggers and it inserts itself again and again because the trigger is triggered when inserted.
I have for example a simple table:
CREATE TABLE example
(
id SERIAL PRIMARY KEY
,name VARCHAR(100) NOT NULL
,session INTEGER
,status VARCHAR(100)
);
My trigger function is:
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
INSERT INTO example VALUES (NEW.id + 1, NEW.name, NEW.session+2, 'blocked');
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';
Trigger is:
CREATE TRIGGER add_block
AFTER INSERT OR UPDATE
ON example
FOR EACH ROW
EXECUTE PROCEDURE add_block();
I get error:
SQL statement "INSERT INTO example VALUES ( $1 +1, $2 , $3 + 2, $4)"
PL/pgSQL function "add_block" line 37 at SQL statement
This error repeats itself so many times that I can't see the top.
How would I solve this?
EDIT:
CREATE TABLE block_rules
(
id SERIAL PRIMARY KEY
,session INTEGER
,block_session INTEGER
);
This table holds the block rules. So if a new record is inserted into the EXAMPLE table with session 1 then it blocks session 3 accordingly by inserting a new record with blocked status in the same (EXAMPLE) table above (not block_rules). Same for session 2 but it blocks session 4.
The block_rules table holds the rules (or pattern) to block a session by. It holds
id | session | block_session
------------------------------
1 | 1 | 3
2 | 2 | 4
3 | 3 | 2
How would I put that in the WHEN statement of the trigger going with Erwin Branstetter's answer below?
Thanks
New answer to edited question
This trigger function adds blocked sessions according to the information in table block_rules.
I assume that the tables are linked by id - information is missing in the question.
I now assume that the block rules are general rules for all sessions alike and link by session. The trigger is only called for non-blocked sessions and inserts a matching blocked session.
Trigger function:
CREATE OR REPLACE FUNCTION add_block()
RETURNS TRIGGER AS
$BODY$
BEGIN
INSERT INTO example (name, session, status)
VALUES (NEW.name
,(SELECT block_session
FROM block_rules
WHERE session = NEW.session)
,'blocked');
RETURN NULL;
END;
$BODY$ LANGUAGE plpgsql;
Trigger:
CREATE TRIGGER add_block
AFTER INSERT -- OR UPDATE
ON example
FOR EACH ROW
WHEN (NEW.status IS DISTINCT FROM 'blocked')
EXECUTE PROCEDURE add_block();
Answer to original question
There is still room for improvement. Consider this setup:
CREATE OR REPLACE FUNCTION add_block()
RETURNS TRIGGER AS
$BODY$
BEGIN
INSERT INTO example (name, session, status)
VALUES (NEW.name, NEW.session + 2, 'blocked');
RETURN NULL;
END;
$BODY$ LANGUAGE plpgsql;
CREATE TRIGGER add_block
AFTER INSERT -- OR UPDATE
ON example
FOR EACH ROW
WHEN (NEW.session < 3)
-- WHEN (status IS DISTINCT FROM 'blocked') -- alternative guess at filter
EXECUTE PROCEDURE add_block();
Major points:
For PostgreSQL 9.0 or later you can use a WHEN condition in the trigger definition. This would be most efficient. For older versions you use the same condition inside the trigger function.
There is no need to add a column, if you can define criteria to discern auto-inserted rows. You did not tell, so I assume that only auto-inserted rows have session > 2 in my example. I added an alternative WHEN condition for status = 'blocked' as comment.
You should always provide a column list for INSERTs. If you don't, later changes to the table may have unexpected side effects!
Do not insert NEW.id + 1 in the trigger manually. This won't increment the sequence and the next INSERT will fail with a duplicate key violation.
id is a serial column, so don't do anything. The default nextval() from the sequence is inserted automatically.
Your description only mentions INSERT, yet you have a trigger AFTER INSERT OR UPDATE. I cut out the UPDATE part.
The keyword plpgsql doesn't have to be quoted.
OK so can't you just add another column, something like this:
ALTER TABLE example ADD COLUMN trig INTEGER DEFAULT 0;
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
IF NEW.trig = 0 THEN
INSERT INTO example VALUES (NEXTVAL('example_id_seq'::regclass), NEW.name, NEW.session+2, 'blocked', 1);
END IF;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';
it's not great, but it works :-)
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
SET SESSION session_replication_role = replica;
INSERT INTO example VALUES (NEXTVAL('example_id_seq'::regclass), NEW.name, NEW.session+2, 'blocked');
SET SESSION session_replication_role = origin;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';