Creating an overdraft statement - mysql

Question

I'm currently stuck on how to create a statement that shows daily overdraft statements for a particular council.
I have the following, councils, users, markets, market_transactions, user_deposits.
market_transaction run daily reducing user's account balance. When the account_balance is 0 the users go into overdraft (negative). When users make a deposit their account balance increases.
I Have put the following tables to show how transactions and deposits are stored.
if I reverse today's transactions I'm able to get what account balance a user had yesterday but to formulate a query to get the daily OD amount is where the problem is.
USERS
user_id
name
account_bal
1
Wells
-5
2
James
100
3
Joy
10
4
Mumbi
-300
DEPOSITS
id
user_id
amount
date
1
1
5
2021-04-26
2
3
10
2021-04-26
3
3
5
2021-04-25
4
4
5
2021-04-25
TRANSACTIONS
id
user_id
amount_tendered
date
1
1
5
2021-04-27
2
2
10
2021-04-26
3
3
15
2021-04-26
4
4
50
2021-04-25
The Relationships are as follows,
COUNCILS
council_id
name
1
a
2
b
3
c
MARKETS
market_id
name
council_id
1
x
3
2
y
1
3
z
2
MARTKET_USER_LINK
id
market_id
user_id
1
1
3
2
2
2
3
3
1
I'm running this SQL query to get the total amount users have spent and subtracting with the current user account balance.
Don't know If I can use this to figure out the account_balance for each day.
SELECT u.user_id, total_spent, total_deposits,m.council_id
FROM users u
JOIN market_user_link ul ON ul.user_id= u.user_id
LEFT JOIN markets m ON ul.market_id =m.market_id
LEFT JOIN councils c ON m.council_id =c.council_id
LEFT JOIN (
SELECT user_id, SUM(amount_tendered) AS total_spent
FROM transactions
WHERE DATE(date) BETWEEN DATE('2021-02-01') AND DATE(NOW())
GROUP BY user_id
) t ON t.user_id= u.user_id
ORDER BY user_id, total_spent ASC
// looks like this when run
| user_id | total_spent | council_id |
|-------------|----------------|------------|
| 1 | 50.00 | 1 |
| 2 | 2.00 | 3 |
I was hoping to reverse transactions and deposits done to get the account balance for a day then get the sum of users with an account balance < 0... But this has just failed to work.
The goal is to produce a query that shows daily overdraft (Only SUM the total account balance of users with account balance below 0 ) for a particular council.
Expected Result
date
council_id
o_d_amount
2021-04-24
1
-300.00
2021-04-24
2
-60.00
2021-04-24
3
-900.00
2021-04-25
1
-600.00
2021-04-25
2
-100.00
2021-04-25
3
-1200.00

Answer 1

This is actually not that hard, but the way you asked makes it hard to follow.
Also, your expected result should match the data you provided.
Edited: Previous solution was wrong - It counted withdraws and deposits more than once if you have more than one event for each user/date.
Start by having the total exchanged on each day, like
select user_id, date, sum(amount) exchanged_on_day from (
select user_id, date, amount amount from deposits
union all select user_id, date, -amount_tendered amount from transactions
) d
group by user_id, date
order by user_id, date;
What follows gets the state of the account only on days that had any deposits or withdraws.
To get the results of all days (and not just those with account movement) you just have to change the cross join part to get a table with all dates you want (like Get all dates between two dates in SQL Server) but I digress...
select dates.date, c.council_id, u.name username
, u.account_bal - sum(case when e.date >= dates.date then e.exchanged_on_day else 0 end) as amount_on_start_of_day
, u.account_bal - sum(case when e.date > dates.date then e.exchanged_on_day else 0 end) as amount_on_end_of_day
from councils c
inner join markets m on c.council_id=m.council_id
inner join market_user_link mul on m.market_id=mul.market_id
inner join users u on mul.user_id=u.user_id
left join (
select user_id, date, sum(amount) exchanged_on_day from (
select user_id, date, amount amount from deposits
union all select user_id, date, -amount_tendered amount from transactions
) d group by user_id, date
) e on u.user_id=e.user_id --exchange on each Day
cross join (select distinct date from (select date from deposits union select date from transactions) datesInternal) dates --all days that had a transaction
group by dates.date, c.council_id, u.name, u.account_bal
order by dates.date desc, c.council_id, u.name;
From there you can rearrange to get the result you want.
select date, council_id
, sum(case when amount_on_start_of_day<0 then amount_on_start_of_day else 0 end) o_d_amount_start
, sum(case when amount_on_end_of_day<0 then amount_on_end_of_day else 0 end) o_d_amount_end
from (
select dates.date, c.council_id, u.name username
, u.account_bal - sum(case when e.date >= dates.date then e.exchanged_on_day else 0 end) as amount_on_start_of_day
, u.account_bal - sum(case when e.date > dates.date then e.exchanged_on_day else 0 end) as amount_on_end_of_day
from councils c
inner join markets m on c.council_id=m.council_id
inner join market_user_link mul on m.market_id=mul.market_id
inner join users u on mul.user_id=u.user_id
left join (
select user_id, date, sum(amount) exchanged_on_day from (
select user_id, date, amount amount from deposits
union all select user_id, date, -amount_tendered amount from transactions
) d group by user_id, date
) e on u.user_id=e.user_id --exchange on each Day
cross join (select distinct date from (select date from deposits union select date from transactions) datesInternal) dates --all days that had a transaction
group by dates.date, c.council_id, u.name, u.account_bal
) result
group by date, council_id
order by date;
You can check it on https://www.db-fiddle.com/f/msScT6B5F7FjU2aQXVr2da/6

Answer 2

Basically the query maps users to councils, caculates periods of overdrafts for users, them aggregates over councils. I assume that starting balance is dated start of the month '2021-04-01' (it could be ending balance as well, see below), change it as needed. Also that negative starting balance counts as an overdraft. For simplicity and debugging the query is divided into a number of steps.
with uc as (
select distinct m.council_id, mul.user_id
from markets m
join market_user_link mul on m.market_id = mul.market_id
),
user_running_total as (
select user_id, date,
coalesce(lead(date) over(partition by user_id order by date) - interval 1 day, date) nxt,
sum(sum(s)) over(partition by user_id order by date) rt
from (
select user_id, date, -amount_tendered s
from transactions
union all
select user_id, date, amount
from deposits
union all
select user_id, se.d, se.s
from users
cross join lateral (
select date(NOW() + interval 1 day) d, 0 s
union all
select '2021-04-01' d, account_bal
) se
) t
group by user_id, date
),
user_overdraft as (
select user_id, date, nxt, least(rt, 0) ovd
from user_running_total
where date <= date(NOW())
),
dates as (
select date
from user_overdraft
union
select nxt
from user_overdraft
),
council__overdraft as (
select uc.council_id, d.date, sum(uo.ovd) total_overdraft, lag(sum(uo.ovd), 1, sum(uo.ovd) - 1) over(partition by uc.council_id order by d.date) prev_ovd
from uc
cross join dates d
join user_overdraft uo on uc.user_id = uo.user_id and d.date between uo.date and uo.nxt
group by uc.council_id, d.date
)
select council_id, date, total_overdraft
from council__overdraft
where total_overdraft <> prev_ovd
order by date, council_id
Really council__overdraft is quite usable, the last step just compacts output excluding intermidiate dates when overdraft is not changed.
With following sample data:
users
user_id name account_bal
1 Wells -5
2 James 100
3 Joy 10
4 Mumbi -300
deposits, odered by date, extra row added for the last date
id user_id amount date
3 3 5 2021-04-25
4 4 5 2021-04-25
1 1 5 2021-04-26
2 3 10 2021-04-26
5 3 73 2021-05-06
transactions, odered by date (note the added row, to illustrate running total in action)
id user_id amount_tendered date
5 4 50 2021-04-25
2 2 10 2021-04-26
3 3 15 2021-04-26
1 1 5 2021-04-27
4 3 17 2021-04-27
councils
council_id name
1 a
2 b
3 c
markets
market_id name council_id
1 x 3
2 y 1
3 z 2
market_user_link
id market_id user_id
1 1 3
2 2 2
3 3 1
4 3 4
the query ouput is
council_id
date
overdraft
1
2021-04-01
0
2
2021-04-01
-305
3
2021-04-01
0
2
2021-04-25
-350
2
2021-04-26
-345
2
2021-04-27
-350
3
2021-04-27
-7
3
2021-05-06
0
Alternatively, provided the users table is holding a closing (NOW()) balance, replace user_running_total CTE with the following code
user_running_total as (
select user_id, date,
coalesce(lead(date) over(partition by user_id order by date) - interval 1 day, date) nxt,
coalesce(sum(sum(s)) over(partition by user_id order by date desc
rows between unbounded preceding and 1 preceding), sum(s)) rt
from (
select user_id, date, amount_tendered s
from transactions
union all
select user_id, date, -amount
from deposits
union all
select user_id, se.d, se.s
from users
cross join lateral (
select date(NOW() + interval 1 day) d, account_bal s
union all
select '2021-04-01' d, 0
) se
) t
where DATE(date) between date '2021-04-01' and date(NOW() + interval 1 day)
group by user_id, date
),
This way the query starts with closing balance dated next date after now and rollouts a running total in the reverse order till '2021-04-01' as a starting date.
Output
council_id
date
overdraft
1
2021-04-01
0
2
2021-04-01
-260
3
2021-04-01
-46
2
2021-04-25
-305
3
2021-04-25
-41
2
2021-04-26
-300
3
2021-04-26
-46
2
2021-04-27
-305
3
2021-04-27
-63
3
2021-05-06
0
db-fiddle both versions