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DDL.sql

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+DROP TABLE ORDER_ITEMS;
+
+DROP TABLE PRODUCTS;
+
+DROP TABLE ORDERS;
+
+DROP TABLE CATEGORIES;
+
+DROP TABLE CUSTOMERS;
+
+--Create the Customers table
+CREATE TABLE CUSTOMERS(
+    CUSTOMER_ID NUMBER PRIMARY KEY,
+    FIRST_NAME VARCHAR(30),
+    LAST_NAME VARCHAR(30),
+    EMAIL VARCHAR(30) UNIQUE,
+    PHONE_NUMBER VARCHAR(20),
+    ADDRESS VARCHAR(40)
+);
+
+-- Create the Categories table
+CREATE TABLE CATEGORIES (
+    CATEGORY_ID NUMBER PRIMARY KEY,
+    CATEGORY_NAME VARCHAR2(50)
+);
+
+-- Create the Orders table
+CREATE TABLE ORDERS (
+    ORDER_ID NUMBER PRIMARY KEY,
+    CUSTOMER_ID NUMBER,
+    ORDER_DATE DATE,
+    TOTAL_PRICE NUMBER(10, 2),
+    FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMERS(CUSTOMER_ID) ON DELETE CASCADE
+);
+
+--Create the Products table
+CREATE TABLE PRODUCTS (
+    PRODUCT_ID NUMBER PRIMARY KEY,
+    PRODUCT_NAME VARCHAR2(30),
+    PRICE NUMBER(10, 2),
+    DESCRIPTION VARCHAR2(100),
+    CATEGORY_ID NUMBER,
+    FOREIGN KEY (CATEGORY_ID) REFERENCES CATEGORIES(CATEGORY_ID) ON DELETE CASCADE
+);
+
+--Create the Order_Items table
+CREATE TABLE ORDER_ITEMS (
+    ORDER_ID NUMBER,
+    PRODUCT_ID NUMBER,
+    QUANTITY NUMBER,
+    UNIT_PRICE NUMBER(10, 2) CHECK(UNIT_PRICE > 0),
+    PRIMARY KEY (ORDER_ID, PRODUCT_ID),
+    FOREIGN KEY (ORDER_ID) REFERENCES ORDERS(ORDER_ID) ON DELETE CASCADE,
+    FOREIGN KEY (PRODUCT_ID) REFERENCES PRODUCTS(PRODUCT_ID) ON DELETE CASCADE
+);
+
+--showing the attributes of all the tables
+DESC CUSTOMERS;
+
+DESCRIBE CATEGORIES;
+
+DESC ORDERS;
+
+DESC ORDER_ITEMS;
+
+--add column in the table
+ALTER TABLE CATEGORIES ADD DESCRIPTION CHAR(20);
+
+--modify domain type of a column
+ALTER TABLE CATEGORIES MODIFY DESCRIPTION VARCHAR(20);
+
+--ramane column
+ALTER TABLE CATEGORIES RENAME COLUMN DESCRIPTION TO CATEGORY_DESC;
+
+--deleting a column
+ALTER TABLE CATEGORIES DROP COLUMN CATEGORY_DESC;
+
+-- computed column
+-- ALTER TABLE Orders
+-- ADD total_price AS (
+--   SELECT SUM(quantity * unit_price)
+--   FROM Order_Items
+--   WHERE order_id = Orders.order_id
+-- );