SQL Query construct - sql-server

Question

I have three tables. I want to get data from all those tables and put it in a virtual table. i am using SQL Server 2012.
Sorry if my format or tags are wrong because I m getting error Stack overflow requires external javascrip from another source domain, which is blocked of failed to load.
Booking Table
BookingId | date
======================
2 | 7/1/2017 (MM/dd/yyyy)
3 | 7/1/2017
BookingCost Table
Id | bookinId | Cost
==========================
1 | 2 | 2000
2 | 3 | 4000
Expense Table
Id | ExpenseCost | Date
======================
1 | 1400 | 7/2/2017 (MM/dd/yyyy)
2 | 1422 | 7/1/2017
3 | 4000 | 6/3/2017
I want to get Monthly result like following Table.
Date | Expense | Bookings
===================================
jan/2017 | 0 | 0
feb/2017 | 0 | 0
. | . | .
. | . | .
. | . | .
jun/2017 | 4000 | 0
jul/2017 | 2822 | 6000
. | . | .
. | . | .
. | . | .

Answer 1

How is something like this (assuming your dates are DATE types and not VARCHAR - otherwise you could convert them).
SELECT COALESCE(EXPENSE.MONTH, BOOKINGS.MONTH) [Date], EXPENSE.Cost Expense, BOOKINGS.Cost Bookings
FROM (
SELECT DATEADD(DD,1-DAY([date]),[date]) MONTH, SUM(Cost) Cost
FROM Booking
INNER JOIN BookingCost
ON Booking.BookingID = BookingCost.BookingID
GROUP BY DATEADD(DD,1-DAY([date]),[date])
) BOOKINGS
FULL JOIN (
SELECT DATEADD(DD,1-DAY([date]),[date]) MONTH, SUM(ExpenseCost) Cost
FROM Expense
GROUP BY DATEADD(DD,1-DAY([date]),[date])
) EXPENSE
ON EXPENSE.MONTH = BOOKINGS.MONTH
ORDER BY 1

Answer 2

To also get the 0 counts, you could left join the totals to a tally table which has all the months for the year.
The sql is using FORMAT to transform the Date
For example:
;WITH MONTHS AS
(
select
[Year], [Month],
format(datefromparts([Year],[Month],1),'MMM/yyyy') as [MonthYear]
from (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12)) m([Month])
cross join (values (2017)) y([Year])
)
select
m.[MonthYear] as [Date],
coalesce(e.TotalExpense,0) as Expense,
coalesce(bc.TotalCost,0) as Bookings
from MONTHS m
left join (
select
datepart(year,[Date]) as [Year],
datepart(month,[Date]) as [Month],
sum(ExpenseCost) as TotalExpense
from Expense
where datepart(year,[Date]) in (select distinct [Year] from MONTHS)
group by datepart(year,[Date]), datepart(month,[Date])
)e on (e.[Year] = m.[Year] and e.[Month] = m.[Month])
left join (
select
datepart(year,b.[date]) as [Year],
datepart(month,b.[date]) as [Month],
sum(c.Cost) as TotalCost
from Booking b
join BookingCost c on c.BookingId = b.BookingId
where datepart(year,b.[date]) in (select distinct [Year] from MONTHS)
group by datepart(year,b.[date]), datepart(month,b.[date])
) bc
on (bc.[Year] = m.[Year] and bc.[Month] = m.[Month])
order by m.[Year], m.[Month];
Test data I used
declare #Booking table (BookingId int, [date] date);
insert into #Booking (BookingId,[date]) values (2,'2017-07-01'),(3,'2017-07-01');
declare #BookingCost table (Id int, BookingId int, Cost int);
insert into #BookingCost (Id, BookingId, Cost) values (1,2,2000),(2,3,4000);
declare #Expense table (Id int, ExpenseCost int, [Date] date);
insert into #Expense (Id, ExpenseCost, [Date]) values
(1,1400,'2017-07-02'),(2,1422,'2017-07-01'),(3,4000,'2017-06-03');