check if values exist in table - trigger - sql

Question

I am trying to write trigger which will control if a record is already in table or not. If is the record already in table (compare for example by name), so current record set valid='False' and insert new. Is there any way?
This is my idea, but it doesn't work.
create or replace TRIGGER
Check_r
before insert on t$customer
FOR each ROW
declare
v_dup number;
v_com number;
v_id number;
v_id_new number;
begin
v_date:=SYSDATE;
select count(id) INTO v_dup from t$customer where surname=:NEW.surname ;
select count(id) INTO v_com from t$customer where firstname =:NEW.firstname and
address=:NEW.address;
select id into v_id from t$customer where surname=:NEW.surname;
if v_dup > 0 and v_com=0 then
v_id_new:= m$_GET_ID; -- get id
update t$customer set valid = 'False' where id = v_id;
insert into t$customer ( id, surname ,firstname, valid, address ) values (v_id_new,:NEW.surname ,:NEW.firstname, :NEW.valid, :NEW.address);
end if;
if v_dup = 0 then
v_id_new:= m$_GET_ID; -- get id
insert into t$customer ( id, surname ,firstname, valid , address) values (v_id_new,:NEW.surname ,:NEW.firstname, :NEW.valid, :NEW.address);
end if;
end;

Answer 1

You can use a compound trigger, for example:
CREATE OR REPLACE TRIGGER Check_r
FOR INSERT ON t$customer
COMPOUND TRIGGER
TYPE customerRecordType IS RECORD(
surname t$customer.surname%TYPE,
firstname t$customer.firstname%TYPE,
address t$customer.address%TYPE,
ID nubmer);
TYPE customerTableType IS TABLE OF customerRecordType;
customerTable customerTableType := customerTableType();
n NUMBER;
BEFORE STATEMENT IS
BEGIN
customerTable.DELETE; -- not requried, just for better understanding
END STATEMENT;
BEFORE EACH ROW IS
BEGIN
customerTable.EXTEND;
customerTable(customerTable.LAST).surname := :NEW.surname;
customerTable(customerTable.LAST).firstname := :NEW.firstname;
customerTable(customerTable.LAST).address := :NEW.address;
customerTable(customerTable.LAST).ID := m$_GET_ID;
:NEW.ID := customerTable(customerTable.LAST).ID;
END BEFORE EACH ROW;
AFTER STATEMENT IS
BEGIN
FOR i IN customerTable.FIRST..customerTable.LAST LOOP
SELECT COUNT(*) INTO n
FROM t$customer
WHERE surname = customerTable(i).surname;
IF n > 1 THEN
UPDATE t$customer
SET valid = 'False'
WHERE surname = customerTable(i).surname;
END IF;
SELECT COUNT(*) INTO n
FROM t$customer
WHERE firstname = customerTable(i).firstname
AND address = customerTable(i).address;
IF n > 1 THEN
UPDATE t$customer
SET valid = 'False'
WHERE firstname = customerTable(i).firstname
AND address = customerTable(i).address
END IF;
END LOOP;
END AFTER STATEMENT;
END;
/
Please note, this solution is ugly and poor in terms of performance!
But it should give you an impression how it works.
In general you should put all this into a PL/SQL Procedure instead of a trigger.

Answer 2

First, this is trigger for insert. you don't need to write insert statement.
Second, you need to update old record. Just update it with your where clause.
CREATE OR REPLACE TRIGGER Check_r
before insert on t$customer
FOR each ROW
BEGIN
UPDATE t$customer set valid = 'False'
WHERE surname = :NEW.surname
AND firstname =:NEW.firstname;
:NEW.id := m$_GET_ID;
END;