PLSQL condition statement in trigger involving 2 tables - sql

Question

I've two tables purchases and customers, I need to update visits_made (number) in customers if time of purchase ptime (date) in purchases table is different from the already existing last_visit (date) in customers table.
Here is the trigger that I'm trying and I'm doing something terribly and shamefully wrong.
create or replace trigger update_visits_made
after insert on purchases
for each row
declare new_date purchases.ptime%type;
begin
select ptime into new_date
from purchases
where purchases.ptime = :new.ptime;
if new_date = customers.last_visit then
new.last_visit=old.last_visit;
else
update customers
set visits_made=visits_made+1
where purchases.ptime=:new.ptime;
end if;
end;
/
show errors
Can anybody please tell me where I'm going wrong?
I get following errors
LINE/COL ERROR
10/15 PLS-00103: Encountered the symbol "=" when expecting one of the
following:
:= . ( # % ;
11/1 PLS-00103: Encountered the symbol "ELSE"
16/1 PLS-00103: Encountered the symbol "END"

Answer 1

This is a scalar assignment in PL/SQL:
new.last_visit = old.last_visit;
Not only should this be done with := but new and old should have colons before their names:
:new.last_visit := :old.last_visit;
Once you have fixed that problem, then the update will pose an issue:
update customers
set visits_made=visits_made+1
where purchases.ptime = :new.ptime;
It is unclear to me what this is supposed to be doing, so I can't suggest anything, other than pointing out that purchases is not defined.

Answer 2

I think somehow i get your requirement. Basically its a ticker which count the vists of user based on Login dates. I have written a snippet below which replicates the same scenario as mentioned Above. Let me know if this helps.
-- Table creation and insertion script
CREATE TABLE PURCHASES
(
P_ID NUMBER,
P_TIME DATE
);
INSERT INTO PURCHASES
SELECT LEVEL,SYSDATE+LEVEL FROM DUAL
CONNECT BY LEVEL < 10;
CREATE TABLE CUSTOMERS
(
P_ID NUMBER,
P_VISITS NUMBER
);
INSERT INTO CUSTOMERS
SELECT LEVEL,NULL FROM DUAL
CONNECT BY LEVEL < 10;
-- Table creation and insertion script
--Trigger Script
CREATE OR REPLACE TRIGGER update_purchase BEFORE
INSERT ON purchases FOR EACH row
DECLARE
new_date purchases.p_time%type;
BEGIN
BEGIN
SELECT A.P_TIME
INTO new_date
FROM
(SELECT p_time,
ROW_NUMBER() OVER(PARTITION BY P_ID ORDER BY P_TIME DESC) RNK
-- INTO new_date
FROM purchases
WHERE purchases.p_id = :new.p_id
)a
WHERE A.RNK =1;
EXCEPTION WHEN OTHERS THEN
RETURN;
END;
IF :NEW.P_TIME <> new_date THEN
UPDATE customers
SET P_VISITS =NVL(P_VISITS,0)+1
WHERE p_id=:new.p_id;
END IF;
END;
--Trigger Script
--Testing Script
INSERT INTO PURCHASES VALUES
(9,TO_DATE('12/11/2015','MM/DD/YYYY'));
--Testing Script