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 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();