feat: triggers added

db/calculation_functions_procedures.sql.sql

@@ -0,0 +1,28 @@
+-- Function to calculate the average author score
+CREATE OR REPLACE FUNCTION fnc_calculate_average_author_score(
+    prc_author_id IN tbl_author.author_id%TYPE,
+    prc_book_rating IN tbl_user_review.book_rating%TYPE
+) RETURN tbl_author.author_score%TYPE 
+IS
+    var_author_score tbl_author.author_score%TYPE;
+    var_sum_rating NUMBER := 0;
+    var_count NUMBER := 0;
+BEGIN
+
+    SELECT SUM(book_rating), COUNT(book_rating)
+    INTO var_sum_rating, var_count
+    FROM tbl_user_review
+    WHERE book_rating IS NOT NULL
+        AND book_id IN (SELECT book_id FROM tbl_book WHERE author_id = prc_author_id);
+
+    IF var_sum_rating IS NULL THEN
+        var_sum_rating := 0;
+    END IF;
+
+    DBMS_OUTPUT.PUT_LINE('Sum: ' || var_sum_rating || ' Count: ' || var_count);
+
+    var_author_score := (var_sum_rating + prc_book_rating)/(var_count + 1);
+
+    RETURN var_author_score;
+END fnc_calculate_average_author_score;
+/

db/dml_triggers.sql

@@ -0,0 +1,98 @@
+-- Function to calculate the average author score
+CREATE OR REPLACE FUNCTION fnc_calculate_average_author_score(
+    prc_author_id IN tbl_author.author_id%TYPE,
+    prc_book_rating IN tbl_user_review.book_rating%TYPE
+) RETURN tbl_author.author_score%TYPE 
+IS
+    var_author_score tbl_author.author_score%TYPE;
+    var_sum_rating NUMBER := 0;
+    var_count NUMBER := 0;
+BEGIN
+
+    SELECT SUM(book_rating), COUNT(book_rating)
+    INTO var_sum_rating, var_count
+    FROM tbl_user_review
+    WHERE book_rating IS NOT NULL
+        AND book_id IN (SELECT book_id FROM tbl_book WHERE author_id = prc_author_id);
+
+    IF var_sum_rating IS NULL THEN
+        var_sum_rating := 0;
+    END IF;
+
+    DBMS_OUTPUT.PUT_LINE('Sum: ' || var_sum_rating || ' Count: ' || var_count);
+
+    var_author_score := (var_sum_rating + prc_book_rating)/(var_count + 1);
+
+    RETURN var_author_score;
+END fnc_calculate_average_author_score;
+/
+
+-- Trigger to update the author score
+CREATE OR REPLACE TRIGGER trg_update_author_score
+BEFORE INSERT ON tbl_user_review
+FOR EACH ROW
+DECLARE
+    var_author_id tbl_author.author_id%TYPE;
+    var_author_score tbl_author.author_score%TYPE;
+BEGIN
+    SELECT author_id
+    INTO var_author_id
+    FROM tbl_book
+    WHERE book_id = :NEW.book_id;
+
+    var_author_score := fnc_calculate_average_author_score(var_author_id, :NEW.book_rating);
+
+    UPDATE tbl_author
+    SET author_score = var_author_score
+    WHERE author_id = var_author_id;
+END trg_update_author_score;
+/
+
+-- Trigger to check the order quantity
+CREATE OR REPLACE TRIGGER trg_check_order_quantity
+BEFORE INSERT ON tbl_order_detail
+FOR EACH ROW
+DECLARE
+    var_available_quantity tbl_book.available_quantity%TYPE;
+    var_book_id tbl_book.book_id%TYPE;
+    var_order_quantity tbl_order_detail.quantity%TYPE;
+BEGIN
+    SELECT available_quantity
+    INTO var_available_quantity
+    FROM tbl_book
+    WHERE book_id = :NEW.book_id;
+
+    IF var_available_quantity < :NEW.quantity THEN
+        RAISE_APPLICATION_ERROR(-20001, 'The quantity ordered is more than the available quantity');
+    END IF;
+
+    UPDATE tbl_book
+    SET available_quantity = var_available_quantity - :NEW.quantity
+    WHERE book_id = :NEW.book_id;
+END trg_check_order_quantity;
+/
+
+-- Trigger to update the order total
+CREATE OR REPLACE TRIGGER trg_update_order_total
+AFTER INSERT ON tbl_order_detail
+FOR EACH ROW
+DISABLE
+DECLARE
+    var_order_id tbl_order_detail.order_id%TYPE;
+    var_order_total tbl_order.total%TYPE;
+BEGIN
+    SELECT order_id
+    INTO var_order_id
+    FROM tbl_order_detail
+    WHERE order_detail_id = :NEW.order_detail_id;
+
+    SELECT SUM(book_price * quantity)
+    INTO var_order_total
+    FROM tbl_order_detail
+    WHERE order_id = var_order_id;
+
+    UPDATE tbl_order
+    SET total = var_order_total
+    WHERE order_id = var_order_id;
+END trg_update_order_total;
+/

db/trigger_function_drops.sql.sql

@@ -0,0 +1,8 @@
+
+DROP TRIGGER trg_update_author_score;
+
+DROP TRIGGER trg_check_order_quantity;
+
+DROP TRIGGER trg_update_order_total;
+
+DROP FUNCTION fnc_calculate_average_author_score;