| 4 | | SELECT |
| 5 | | SUM(tb.spent_amount) AS total_spent |
| 6 | | FROM |
| 7 | | transaction_breakdown tb |
| 8 | | JOIN transaction t ON tb.transaction_id = t.transaction_id |
| 9 | | JOIN transaction_account ta ON tb.transaction_account_id = ta.transaction_account_id |
| 10 | | WHERE |
| 11 | | ta.user_id = 101 -- ID на конкретниот корисник |
| 12 | | AND EXTRACT(MONTH FROM t.date) = EXTRACT(MONTH FROM CURRENT_DATE) |
| 13 | | AND EXTRACT(YEAR FROM t.date) = EXTRACT(YEAR FROM CURRENT_DATE); |
| | 4 | CREATE OR REPLACE FUNCTION get_total_spent_current_month_user( |
| | 5 | p_user_id INT |
| | 6 | ) |
| | 7 | RETURNS TABLE ( |
| | 8 | total_spent NUMERIC |
| | 9 | ) |
| | 10 | LANGUAGE plpgsql |
| | 11 | AS $$ |
| | 12 | BEGIN |
| | 13 | RETURN QUERY |
| | 14 | SELECT |
| | 15 | COALESCE(SUM(tb.spent_amount), 0) AS total_spent |
| | 16 | FROM transaction_breakdown tb |
| | 17 | JOIN transaction t |
| | 18 | ON tb.transaction_id = t.transaction_id |
| | 19 | JOIN transaction_account ta |
| | 20 | ON tb.transaction_account_id = ta.transaction_account_id |
| | 21 | WHERE ta.user_id = p_user_id |
| | 22 | AND EXTRACT(MONTH FROM t.date) = EXTRACT(MONTH FROM CURRENT_DATE) |
| | 23 | AND EXTRACT(YEAR FROM t.date) = EXTRACT(YEAR FROM CURRENT_DATE); |
| | 24 | END; |
| | 25 | $$; |
| | 27 | |
| | 28 | ==== Релациона алгебра |
| | 29 | - TA(transaction_account_id, user_id) |
| | 30 | - TB(transaction_id, transaction_account_id, spent_amount) |
| | 31 | - T(transaction_id, date) |
| | 32 | |
| | 33 | JOIN на сите табели: |
| | 34 | - J1 ← TA ⨝,,TA.transaction_account_id = TB.transaction_account_id,, TB |
| | 35 | - J2 ← J1 ⨝,,TB.transaction_id = T.transaction_id,, T |
| | 36 | |
| | 37 | Филтрирање на трансакции за даден корисник и тековен месец: |
| | 38 | - F ← σ,,user_id = p_user_id ∧ EXTRACT(MONTH FROM date) = EXTRACT(MONTH FROM CURRENT_DATE) ∧ EXTRACT(YEAR FROM date) = EXTRACT(YEAR FROM CURRENT_DATE),, (J2) |
| | 39 | |
| | 40 | Агрегација на вкупно потрошено: |
| | 41 | - R_final ← γ,,; SUM(spent_amount) → total_spent,,(F) |