SQL query to compare budget to actual expenses - sql

Question

I'm struggling to build a query comparing budget to actual expense items.
The budget table has a single record per month/category on the first day of the month whereas the expense table has many records throughout the days of the month.
My desired result:
YEAR
MONTH
category
budgetAmt
sumExpenseAmt
2021
1
daily
100
49
2021
1
monthly
42
87
2021
2
daily
101
36
2021
2
monthly
55
82
What I'm getting:
YEAR
MONTH
category
budgetAmt
sumExpenseAmt
2021
1
daily
100
85
2021
1
monthly
42
169
2021
2
daily
101
85
2021
2
monthly
55
169
The amounts in "sumExpenseAmt" are wrong AND they're repeating.
(85 is the sum of all expense-daily items (jan + feb): 40 + 9 + 32 + 4)
(169 is the sum of all expense-monthly items (jan + feb): 83 + 4 + 75 +7)
MY SQL:
SELECT YEAR( "b"."date" ) AS "Year"
, MONTH( "b"."date" ) AS "Month"
, "b"."category"
, "b"."budgetAmt"
, SUM( "e"."expenseAmt" ) AS "sumExpenseAmt"
FROM "budget" AS "b"
JOIN "expense" AS "e" ON "b"."category" = "e"."category"
GROUP BY YEAR( "b"."date" ), MONTH( "b"."date" ), "b"."category", "b"."budgetAmt"
table: budget
date
category
budgetAmt
2021-01-01
daily
100
2021-01-01
monthly
42
2021-02-01
daily
101
2021-02-01
monthly
55
table: expense
date
category
expenseAmt
2021-01-04
daily
40
2021-01-07
daily
9
2021-01-08
monthly
83
2021-01-25
monthly
4
2021-02-01
daily
32
2021-02-05
daily
4
2021-02-15
monthly
75
2021-02-20
monthly
7
I've tried aggregating the expense table with a query and feeding the result into my initial SQL query, but that gives me the same result.
query: qry_summary_expense
date
category
budgetAmt
2021-01-01
daily
49
2021-01-01
monthly
87
2021-02-01
daily
36
2021-02-01
monthly
82
SELECT YEAR( "b"."date" ) AS "Year"
, MONTH( "b"."date" ) AS "Month"
, "b"."category", "b"."budgetAmt"
, SUM( "e"."expenseAmt" ) AS "sumExpenseAmt"
FROM "budget" AS "b"
JOIN "qry_summary_expense" AS "e" ON "b"."category" = "e"."category"
GROUP BY YEAR( "b"."date" ), MONTH( "b"."date" ), "b"."category", "b"."budgetAmt"

Answer 1

I'd join on both month and category
select year(b.date) as year,
month(b.date) as month,
b.category,
avg(budgetAmt) as budgetAmt,
sum(expenseAmt) as expenseAmt
from expense e
join budget b
on (month(b.date) = month(e.date)
and b.category = e.category)
group by year(b.date), month(b.date), b.category

Answer 2

You need to join the two tables on category AND month (using eomonth (end of month) does the trick).
SELECT Year(Eomonth(e.date)) AS year,
Month(Eomonth(e.date)) AS month,
e.category,
Avg(budgetamt) AS budgetAmt,
Sum(expenseamt) AS sumExpenseAmt
FROM expense e
INNER JOIN budget b
ON Eomonth(e.date) = Eomonth(b.date)
AND e.category = b.category
GROUP BY e.category,
Eomonth(e.date);
Fiddle

Answer 3

Alternatively you can use left or right joins based on your need.
select b.Year,b.Month,b.category,Budget, Expenses
from(
Select year(date) [Year] ,month(date) [Month] ,category,sum(budgetAmt) Budget
from budget
group by year(date),month(date),category
) b
Join
(
Select year(date) [Year] ,month(date) [Month] ,category,sum(expenseAmt) Expenses
from expense
group by year(date),month(date),category
) e
on b.Month = e.Month and b.Year = e.Year and b.category = e.category
Another Approach Using EOMONTH Function:
select Year(a.dates) Year ,month(a.dates) Month,a.category,sum(Budget) Budget, sum(Expenses) Expenses
from(
Select EOMONTH(date) dates,category,sum(budgetAmt) Budget
from #budget
group by EOMONTH(date),category
) a
Join
(
Select EOMONTH(date) dates,category,sum(expenseAmt) Expenses
from #expense
group by EOMONTH(date),category
) b
on a.dates = b.dates and a.category = b.category
group by Year(a.dates),month(a.dates),a.category