ORACLE SQL Problem 2

Given the following tables and data:

create table months (monthIndex int);

create table invoice(invoiceId int, month int)

create table lineitems(lid int, invoiceID int, charged_amount decimal(6,2), contracted_rate decimal(6,2))

Insert into months values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12);

Insert into invoice values

(1,1), (2,1), (3,2) (4,2), (5,4), (6,5), (7,5), (8,8), (9,8), (10,3), (11,3), (12,6), (13,7), (14,10), (15,11), (16,11);

Insert into lineitems values

(1,1,1000.10,1000.10),

(2,1,1500.20,1200.00),

(3,1,1300.10,1300.10),

(4,2,2100.30,2100.30),

(5,2,1100.10,1000.10),

(6,2,1100.40,1100.40),

(7,3,6000.10,6000.40),

(8,3,1400.10,1400.40),

(9,4,4500.10,4500.10),

(10,5,3300.10,3000.18),

(11,5,2900.10,2900.10),

(12,6,8900.10,8900.10),

(13,6,2200.10,2200.10),

(14,8,3700.10,3700.50),

(15,9,7000.10,7000.60),

(16,10,2200.10,2200.10),

(17,10,2200.10,2200.10),

(18,11,2200.10,2200.10),

(19,12,2200.10,2200.10),

(20,13,2200.10,2200.10),

(21,13,2200.10,2200.10),

(22,14,1100.10,1000.10),

(23,14,1100.40,1100.40),

(24,14,6000.10,6000.40),

(25,15,1400.10,1400.40),

(26,16,4500.10,4500.10),

(27,16,3300.10,3000.18);

Develop a single SQL Query that computes the total invoices amount for each month , and the percentage of change from the previous month. If there are no invoices for the month , the computed value should be null.

Here is the result that the query should generate: