= Оптимизиран SQL-код, кој работи поедноставно и побрзо


== DDL код
{{{
create table account(
    id serial primary key,
    username varchar(255) not null,
    email varchar(255) not null,
    password varchar(255) not null,
    balance decimal(15, 2) not null 
);

create table "transaction"(
    id serial primary key,
    amount decimal(15, 2) not null,
    currency varchar(255) not null,
    type varchar(50) not null,
    timestamp timestamp default current_timestamp,
    account_id int not null,
    foreign key (account_id) references account(id)
);

create table transfer(
    id serial primary key,
    s_id int not null,
    r_id int not null, 
    foreign key(s_id) references account(id),
    foreign key(r_id) references
    account(id)

);

create table deposit(
    id serial primary key,
    account_id int not null,
    transaction_id int not null,
    amount decimal(15,2) not null,
    foreign key(account_id) references account(id),
    foreign key(transaction_id) references transaction(id)
);

create table withdraw(
    id serial primary key,
    account_id int not null,
    transaction_id int not null,
    amount decimal(15,2) not null,
    foreign key(account_id) references account(id),
    foreign key(transaction_id) references transaction(id)
);

create table transferred_money(
    id serial primary key, 
    s_account_id int not null, 
    r_account_id int not null, 
    t_id int not null, 
    currency varchar(50) not null, 
    foreign key (s_account_id) references account(id),
    foreign key (r_account_id) references account(id),
    foreign key (t_id) references transaction(id)
);

}}}


== Trigger 1
{{{
create or replace function after_transaction_trigger()
returns trigger as $$
begin

	if new.type = 'Deposit' then
		insert into Deposit(account_id, id, amount)
		values (new.account_id, new.id, new.amount);
	
	elsif new.type = 'Withdrawal' then
		insert into Deposit(account_id, id, amount)
		values (new.account_id, new.id, new.amount);
	
	elsif new.type like '(MKD) Transfer Out to%' then
		insert into transferred_money(s_account_id, r_account_id, t_id, currency)
		select new.account_id, (select id from account where username = trim(substring(new.type from position('Transfer Out to ' in new.type)+15)) limit 1),
			new.id, new.currency; 

	elsif new.type like '(USD) Transfer Out to%' then
		insert into transferred_money(s_account_id, r_account_id, t_id, currency)
		select new.account_id, (select id from account where username = trim(substring(new.type from position('Transfer Out to ' in new.type)+15)) limit 1),
			new.id, new.currency;
	
	elsif new.type like '(EUR) Transfer Out to%' then
		insert into transferred_money(s_account_id, r_account_id, t_id, currency)
		select new.account_id, (select id from account where username = trim(substring(new.type from position('Transfer Out to ' in new.type)+15)) limit 1),
			new.id, new.currency;
			
	elsif new.type like '(GBP) Transfer Out to%' then
		insert into transferred_money(s_account_id, r_account_id, t_id, currency)
		select new.account_id, (select id from account where username = trim(substring(new.type from position('Transfer Out to ' in new.type)+15)) limit 1),
			new.id, new.currency;

	end if;
	return new;
end;
$$ language plpgsql;

create trigger after_transaction
after insert on transaction
for each row
execute function after_transaction_trigger();
}}}


== Trigger 2

{{{


CREATE OR REPLACE FUNCTION after_transaction_trigger2()
RETURNS TRIGGER AS $$
BEGIN
    IF NEW.type = 'Deposit' THEN
        -- Log deposit as a self-transfer
        INSERT INTO transfer(s_id, r_id)
        VALUES (NEW.account_id, NEW.account_id);

    ELSIF NEW.type = 'Withdrawal' THEN
        -- Log withdrawal as a self-transfer
        INSERT INTO transfer(s_id, r_id)
        VALUES (NEW.account_id, NEW.account_id);

    ELSIF NEW.type LIKE '(MKD) Transfer Out to%' OR 
          NEW.type LIKE '(USD) Transfer Out to%' OR 
          NEW.type LIKE '(EUR) Transfer Out to%' OR 
          NEW.type LIKE '(GBP) Transfer Out to%' THEN
          
        -- Extract recipient username and insert into transfer table
        INSERT INTO transfer(s_id, r_id)
        SELECT NEW.account_id, 
               (SELECT id FROM account 
                WHERE username = TRIM(SUBSTRING(NEW.type FROM POSITION('Transfer Out to ' IN NEW.type) + 15)) 
                LIMIT 1);

    END IF;
    
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER after_transaction2
AFTER INSERT ON transaction
FOR EACH ROW
EXECUTE FUNCTION after_transaction_trigger2();

}}}


== Прикажи ги корисниците со најголем број на трансфери на пари(број на с-ка, корисничко име, e-mail, број на трансфери и ранг во растечки редослед)

{{{
WITH transfer_frequency AS (
    SELECT t.s_id AS account_id, COUNT(*) AS transfer_count
    FROM transfer t
    GROUP BY t.s_id

    UNION ALL

    SELECT t.r_id AS account_id, COUNT(*) AS transfer_count
    FROM transfer t
    GROUP BY t.r_id
)

SELECT *
FROM (
    SELECT a.id AS account_id,
           a.username,
           a.email,
           tf.transfer_count,
           RANK() OVER (ORDER BY tf.transfer_count DESC) AS transfer_rank
    FROM account a
    JOIN transfer_frequency tf ON a.id = tf.account_id
) ranked_accounts
WHERE transfer_rank <= 3
ORDER BY transfer_rank;


}}}

== Корисници кои направиле најголеми или примиле најголеми износи на трансфери и вкупен износ на трансфери(број на с-ка, корисничко име, e-mail, вкупен износ на сите трансфери по корисник и ранг на корисник во растечки редослед)

{{{
WITH transfer_amount AS (
    SELECT t.s_id AS account_id, SUM(tr.amount) AS total_transfer
    FROM transfer t
    JOIN "transaction" tr ON t.id = tr.id
    GROUP BY t.s_id

    UNION ALL

    SELECT t.r_id AS account_id, SUM(tr.amount) AS total_transfer
    FROM transfer t
    JOIN "transaction" tr ON t.id = tr.id
    GROUP BY t.r_id
),

aggregated_transfers AS (
    SELECT account_id, SUM(total_transfer) AS total_transfer_amount
    FROM transfer_amount
    GROUP BY account_id
)

SELECT a.id AS account_id,
       a.username,
       a.email,
       COALESCE(at.total_transfer_amount, 0) AS total_transfer_amount,
       RANK() OVER (ORDER BY COALESCE(at.total_transfer_amount, 0) DESC) AS transfer_rank
FROM account a
LEFT JOIN aggregated_transfers at ON a.id = at.account_id
ORDER BY transfer_rank
LIMIT 3; 
}}}

== Корисници со највисок износ на депозити

{{{

WITH deposit_totals AS (
    SELECT account_id, SUM(amount) AS total_deposit
    FROM deposit
    GROUP BY account_id
)

SELECT a.id AS account_id,
       a.username,
       a.email,
       COALESCE(dt.total_deposit, 0) AS total_deposit,
       RANK() OVER (ORDER BY COALESCE(dt.total_deposit, 0) DESC) AS deposit_rank
FROM account a
LEFT JOIN deposit_totals dt ON a.id = dt.account_id
ORDER BY deposit_rank
LIMIT 3; 
}}}


== Најактивните корисници во последните 30 дена
{{{
WITH recent_activity AS (
    SELECT account_id, COUNT(*) AS activity_count
    FROM "transaction"
    WHERE timestamp >= NOW() - INTERVAL '30 days'
    GROUP BY account_id
)

SELECT a.id AS account_id,
       a.username,
       a.email,
       COALESCE(ra.activity_count, 0) AS recent_transactions
FROM account a
LEFT JOIN recent_activity ra ON a.id = ra.account_id
ORDER BY recent_transactions DESC
LIMIT :top_n;



}}}