views

Author: ptyadana

Complete SQL Mastery - Mosh/08.Views.sql

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+/*****************************************/
+/*  Creating Views                       */
+/*****************************************/
+
+USE mosh_sql_invoicing;
+
+CREATE VIEW v_sales_by_client AS (
+	SELECT c.client_id, c.name, SUM(invoice_total) AS total_sales
+	FROM clients c
+	JOIN invoices i USING (client_id)
+	GROUP BY client_id, name
+);
+
+SELECT *
+FROM v_sales_by_client;
+
+/*view to see the balance for each client.*/
+CREATE OR REPLACE VIEW v_clients_balance AS (
+	SELECT c.client_id, c.name, SUM(i.invoice_total - i.payment_total) AS balance
+	FROM clients c
+	JOIN invoices i ON c.client_id = i.client_id
+	GROUP BY 1
+);
+
+/*****************************************/
+/*  Altering or Dropping Views           */
+/*****************************************/
+
+DROP VIEW v_sales_by_client;
+
+CREATE OR REPLACE VIEW v_clients_balance AS (
+	SELECT c.client_id, c.name, SUM(i.invoice_total - i.payment_total) AS balance
+	FROM clients c
+	JOIN invoices i ON c.client_id = i.client_id
+	GROUP BY 1
+);
+
+
+/*****************************************/
+/*  Updatable  Views                     */
+/*****************************************/
+
+CREATE VIEW v_invoices_with_remaining_balance AS (SELECT invoice_id, number, client_id, invoice_total, payment_total,
+	invoice_total - payment_total AS remaining_balance,
+	invoice_date, due_date, payment_date
+FROM invoices);
+
+SELECT * FROM v_invoices_with_remaining_balance;
+
+-- delete
+DELETE FROM v_invoices_with_remaining_balance
+WHERE invoice_id = 1;
+
+-- update 
+UPDATE v_invoices_with_remaining_balance
+SET due_date = '2020-01-01'
+WHERE invoice_id = 2; 
+
+
+/*****************************************/
+/*  WITH OPTION CHECK Clause             */
+/*****************************************/
+/*To ensure the consistency of a view so that users can only display or update data that visible through the view, 
+you use the WITH CHECK OPTION when you create or modify the view.*/
+
+CREATE OR REPLACE VIEW v_invoices_with_remaining_balance AS (SELECT invoice_id, number, client_id, invoice_total, payment_total,
+	invoice_total - payment_total AS remaining_balance,
+	invoice_date, due_date, payment_date
+FROM invoices
+WHERE (invoice_total - payment_total) > 0
+) WITH CHECK OPTION;
+
+SELECT * FROM v_invoices_with_remaining_balance;
+
+UPDATE v_invoices_with_remaining_balance
+SET payment_total = invoice_total
+WHERE invoice_id = 2;