Two classic SQL statements related to dates

Statement
1. What is the maximum number of days of the month in which a date is obtained with a statement?

SELECT Day (DATEADD (DD,-day (' 2004-02-13 '), DATEADD (mm, 1, ' 2004-02-13 '))-as ' Day number '




2. Fewer records become multiple records problems

There are table TBL
Date Income expenditure
2004-02-11 00:00:00 60 45
2004-03-01 00:00:00 60 45
2004-03-02 00:00:00 40 50
2004-03-05 00:00:00 50 40

/*
Test data:
Create Table TBL ([date] smalldatetime,[revenue] int, [expense] int)

Insert into TBL
SELECT ' 2004-02-11 ', 60, 45
Union SELECT ' 2004-03-01 ', 60, 45
Union SELECT ' 2004-03-02 ', 40, 50
Union SELECT ' 2004-03-05 ', 50, 40
*/

The results to be obtained:
Date income expense balance
2004-02-01 00:00:00 null NULL NULL
2004-02-02 00:00:00 null NULL NULL
2004-02-03 00:00:00 null NULL NULL
2004-02-04 00:00:00 null NULL NULL
2004-02-05 00:00:00 null NULL NULL
2004-02-06 00:00:00 null NULL NULL
2004-02-07 00:00:00 null NULL NULL
2004-02-08 00:00:00 null NULL NULL
2004-02-09 00:00:00 null NULL NULL
2004-02-10 00:00:00 null NULL NULL
2004-02-11 00:00:00 60 45 15
2004-02-12 00:00:00 NULL NULL 15
2004-02-13 00:00:00 NULL NULL 15
2004-02-14 00:00:00 NULL NULL 15
2004-02-15 00:00:00 NULL NULL 15
2004-02-16 00:00:00 NULL NULL 15
2004-02-17 00:00:00 NULL NULL 15
2004-02-18 00:00:00 NULL NULL 15
2004-02-19 00:00:00 NULL NULL 15
2004-02-20 00:00:00 NULL NULL 15
2004-02-21 00:00:00 NULL NULL 15
2004-02-22 00:00:00 NULL NULL 15
2004-02-23 00:00:00 NULL NULL 15
2004-02-24 00:00:00 NULL NULL 15
2004-02-25 00:00:00 NULL NULL 15
2004-02-26 00:00:00 NULL NULL 15
2004-02-27 00:00:00 NULL NULL 15
2004-02-28 00:00:00 NULL NULL 15
2004-02-29 00:00:00 NULL NULL 15
2004-03-01 00:00:00 60 45 30
2004-03-02 00:00:00 40 50 20
2004-03-03 00:00:00 NULL NULL 20
2004-03-04 00:00:00 NULL NULL 20
2004-03-05 00:00:00 50 40 30
2004-03-06 00:00:00 NULL NULL 30
2004-03-07 00:00:00 NULL NULL 30
2004-03-08 00:00:00 NULL NULL 30
2004-03-09 00:00:00 NULL NULL 30
2004-03-10 00:00:00 NULL NULL 30
2004-03-11 00:00:00 NULL NULL 30
2004-03-12 00:00:00 NULL NULL 30
2004-03-13 00:00:00 NULL NULL 30
2004-03-14 00:00:00 NULL NULL 30
2004-03-15 00:00:00 NULL NULL 30
2004-03-16 00:00:00 NULL NULL 30
2004-03-17 00:00:00 NULL NULL 30
2004-03-18 00:00:00 NULL NULL 30
2004-03-19 00:00:00 NULL NULL 30
2004-03-20 00:00:00 NULL NULL 30
2004-03-21 00:00:00 NULL NULL 30
2004-03-22 00:00:00 NULL NULL 30
2004-03-23 00:00:00 NULL NULL 30
2004-03-24 00:00:00 NULL NULL 30
2004-03-25 00:00:00 NULL NULL 30
2004-03-26 00:00:00 NULL NULL 30
2004-03-27 00:00:00 NULL NULL 30
2004-03-28 00:00:00 NULL NULL 30
2004-03-29 00:00:00 NULL NULL 30
2004-03-30 00:00:00 NULL NULL 30
2004-03-31 00:00:00 NULL NULL 30

Answer:
SELECT y.[Date], tbl. [Income], tbl. [Expenditure], (
SELECT SUM (ISNULL (tbl.[ Revenue], 0)-isnull (tbl.[ Expenses], 0)) from TBL WHERE [date]<=y.[Date]) as [balance]
From TBL Right JOIN (
SELECT DATEADD (DD, N.I, DATEADD (DD, 1-day (m.minday), m.minday)) as [date]
From (
SELECT 0 As I
UNION all SELECT 1
UNION All SELECT 2
UNION All SELECT 3
UNION All SELECT 4
UNION all SELECT 5
UNION All SELECT 6
UNION All SELECT 7
UNION All SELECT 8
UNION All SELECT 9
UNION All SELECT 10
UNION All SELECT 11
UNION All SELECT 12
UNION All SELECT 13
UNION All SELECT 14
UNION All SELECT 15
UNION All SELECT 16
UNION all SELECT 17
UNION All SELECT 18
UNION all SELECT 19
UNION All SELECT 20
UNION All SELECT 21
UNION all SELECT 22
UNION all SELECT 23
UNION All SELECT 24
UNION all SELECT 25
UNION all SELECT 26
UNION all SELECT 27
UNION all SELECT 28
UNION all SELECT 29
UNION All SELECT 30
UNION all SELECT 31
N
(
SELECT MIN (date) as Minday
From TBL
GROUP by DATEDIFF (month, 0, date)
) M
WHERE DATEDIFF (MM, DATEADD (DD, N.I, DATEADD (DD, 1-day (m.minday), M.minday)), M.minday) =0) as Y
On TBL. [Date]=y. Date