Files updated

Lesson08/Exercise6_functions.sql

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+DROP FUNCTION get_stock;
+CREATE FUNCTION get_stock(TEXT) RETURNS integer AS $stock_val$
+DECLARE stock_val integer;
+BEGIN
+    SELECT stock INTO stock_val FROM products WHERE product_code=$1;
+RETURN stock_val;
+END; $stock_val$
+LANGUAGE PLPGSQL;
+
+DROP FUNCTION update_stock;
+CREATE FUNCTION update_stock() RETURNS integer AS $stock_qty$
+DECLARE
+    stock_qty integer;
+    _order_id integer;
+    _prod_code TEXT;
+BEGIN
+    SELECT max(order_id) INTO _order_id FROM order_info; 
+    SELECT qty INTO stock_qty FROM order_info WHERE order_id= _order_id;
+    SELECT product_code INTO _prod_code FROM order_info WHERE order_id=_order_id;
+    stock_qty := get_stock(_prod_code) - stock_qty;
+    UPDATE products SET stock = stock_qty WHERE product_code=_prod_code; 
+RETURN stock_qty;
+END; $stock_qty$
+LANGUAGE PLPGSQL;
+
+DROP FUNCTION insert_order;
+CREATE FUNCTION insert_order(integer, TEXT, integer) RETURNS integer AS $new_order_id$
+DECLARE
+   new_order_id integer;
+BEGIN
+    SELECT MAX(order_id) INTO new_order_id FROM order_info;
+    new_order_id := new_order_id + 1;
+    INSERT INTO order_info (order_id, customer_id, product_code, qty) VALUES
+        (new_order_id, $1, $2, $3);
+RETURN new_order_id;
+END; $new_order_id$
+LANGUAGE PLPGSQL;