Select With Multiple Where Criteria - sql

I'm trying to do a select for a whole series of different criteria. I'm essentially going to take today's date, and use it against our invoice table to figure out how we're shaping up this year, compared to the last several years.
In the end, I essentially want to have columns for Year, Year To Date Sales, Quarter To Date Sales, and Month to Date Sales. I've started to create a loop for this, but the problem I'm running into is that it's executing several select's, and not returning me one dataset, but rather 3.
Is the best way to tackle this to build a virtual table, fill it with my results, and then select them out of that?
Here's what I have so far:
DECLARE #startDate date, #endDate date;
DECLARE #counter int = 0;
WHILE #counter < 3 BEGIN
--set start and end dates
SELECT #startDate = CONVERT(date, (CONVERT(nvarchar, YEAR(DATEADD(YEAR,-1 * #counter, CONVERT(date, GETDATE())))) + '-02-01'));
SELECT #endDate = DATEADD(YEAR,-1 * #counter, CONVERT (date, GETDATE()));
--select results
SELECT YEAR(ib.DateDelivered) [Year], SUM(ib.TotalAmountLessFreight) [YTD Sale]
FROM InvoiceBase ib
WHERE ib.DateDelivered < #endDate
AND ib.DateDelivered > #startDate
GROUP BY YEAR(ib.DateDelivered);
--increment
SET #counter = #counter + 1;
END


The best way to do it would be in a single query. Try:
;with cte as
(select i.*,
dateadd(year, datediff(year,DateDelivered,getdate()), getdate()) [YearEnd]
FROM InvoiceBase i)
select YEAR(DateDelivered) [Year],
SUM(case when DateDelivered <= YearEnd
then TotalAmountLessFreight end) [YTD Sales],
SUM(case when DateDelivered <= YearEnd and
month(DateDelivered) >= floor((month(YearEnd)+2)/3)*3-2
then TotalAmountLessFreight end) [QTD Sales],
SUM(case when DateDelivered <= YearEnd and
datediff(month, DateDelivered, YearEnd) = 0
then TotalAmountLessFreight end) [MTD Sales]
FROM cte
GROUP BY YEAR(DateDelivered)

Related

Calculate total and elapsed number of working days in the month for a given date

I am stuck with a SQL query.
I am trying to calculate two different things in a same query:
Number of business days in a month (this will exclude weekends).
How many days working days have been passed in a month.
Let's say for November (as on 11/9/2018)
no.of business days no. of business days passed
22 7
I tried like this :
WITH cteAllDates AS
(
DECLARE #StartDate DATETIME
DECLARE #EndDate DATETIME
SET #StartDate = '10/01/2018'
SET #EndDate = '10/31/2018'
SELECT
(DATEDIFF(dd, #StartDate, #EndDate) + 1)
- (DATEDIFF(wk, #StartDate, #EndDate) * 2)
- (CASE WHEN DATENAME(dw, #StartDate) = 'Sunday' THEN 1 ELSE 0 END)
- (CASE WHEN DATENAME(dw, #EndDate) = 'Saturday' THEN 1 ELSE 0 END) AS x
) AS y
SELECT x
FROM cteAllDates
I would like to create a virtual table so that I can use these fields in my complete query. And if its possible I can do this with GETDATE() and not to declare dates every time.

Since you want to do it in a CTE, and based on the earlier answer you found on SO, here is a version that does it all for the current month without needing to define start and end dates:
EDIT: To create a holiday table
First, create a holiday table. Don't do this every time, make it a persistent table, and keep it filled up with all holidays you need - easter, xmas etc.
create table holidays(holiday date)
insert holidays values ('2018-09-23'),('2018-09-24')
Now the query, including the check for number of holidays between the dates
;with dates as(
select dateadd(d,-day(getdate())+1,convert(date,getdate())) as startofmonth,
dateadd(d,-1,dateadd(m,1,dateadd(d,-day(getdate())+1,convert(date,getdate())))) as endofmonth,
convert(date,getdate()) as today
)
,holidaycount as (
select count(*) as holidaysinmonth,
sum(case when holiday<=today then 1 else 0 end) as holidaystodate
from dates
join holidays on holiday between startofmonth and endofmonth
)
,daycounts as(
select dates.*,
(DATEDIFF(dd, startofmonth, endofmonth) + 1)
-(DATEDIFF(wk, startofmonth, endofmonth) * 2)
-(CASE WHEN DATENAME(dw, startofmonth) = 'Sunday' THEN 1 ELSE 0 END)
-(CASE WHEN DATENAME(dw, endofmonth) = 'Saturday' THEN 1 ELSE 0 END)
-isnull(holidaysinmonth,0) as wkdaysinmonth,
(DATEDIFF(dd, startofmonth, today) + 1)
-(DATEDIFF(wk, startofmonth, today) * 2)
-(CASE WHEN DATENAME(dw, startofmonth) = 'Sunday' THEN 1 ELSE 0 END)
-(CASE WHEN DATENAME(dw, today) = 'Saturday' THEN 1 ELSE 0 END)
-isnull(holidaystodate,0) as wkdaystodate
from dates
cross join holidaycount
)
select * from daycounts
EDIT: If you cant create a temp table, add this as an additional CTE before the holidaycount one like so:
,holidays as (
select holiday from (values ('2018-11-23'),('2018-11-24')) t(holiday)
)
,holidaycount as (

You can try to use cte recursive make a calendar table, then use condition aggregate function to get your result.
DECLARE #StartDate DATETIME
DECLARE #EndDate DATETIME
SET #StartDate = DATEADD(DAY, 1, EOMONTH(GETDATE(), -1));
SET #EndDate = DATEADD(DAY, 1, EOMONTH(GETDATE()));
;WITH CTE AS (
select #StartDate startdt,#EndDate enddt
UNION ALL
SELECT DATEADD (day ,1 , startdt) , #EndDate
FROM CTE
WHERE DATEADD (day,1,startdt) <= #EndDate
)
select SUM(CASE WHEN DATENAME(dw, startdt) NOT IN ('Sunday','Saturday') THEN 1 END) 'no.of business days',
SUM(CASE WHEN DATENAME(dw, startdt) NOT IN ('Sunday','Saturday') AND GETDATE() >= startdt THEN 1 END) 'no. of business days passed'
FROM CTE
sqlfiddle
Result
no.of business days no. of business days passed
22 7

Number of working days between two dates

I want number of working days in between to dates. For example if we have 01-01-2012 and 20-01-2012, i want to get the number of working days in between that two dates using T-SQL.

Since SQL Server has no idea what your company considers working days, the best answer to this problem is likely going to be to use a calendar table. Once you have a table with past and future dates, with a column like IsWorkDay correctly updated, the query is simple:
SELECT [Date] FROM dbo.Calendar
WHERE [Date] >= #start
AND [Date] <= #end
AND IsWorkDay = 1;

DECLARE #fromDate datetime, #toDate datetime
SELECT #fromDate = ' 01-01-2012', #toDate = '20-01-2012'
SELECT (DATEDIFF(day, #fromDate, #toDate) + 1)
- (DATEDIFF(week, #fromDate, #toDate) * 2)
- (CASE WHEN DATENAME(weekday, #fromDate) = 'Sunday' THEN 1 ELSE 0 END)
- (CASE WHEN DATENAME(weekday, #toDate) = 'Saturday' THEN 1 ELSE 0 END)

I liked Aaron Bertrand's suggestion so I wrote this code that can be added to your queries. It creates a table variable between 2 dates that you can then use in your query by joining on the CalendarDate column (just remember to strip out any time information before joining). This is based on the typical American work week of Monday through Friday.
DECLARE #StartDate DATE
DECLARE #EndDate DATE
SET #StartDate = '2013-08-19'
SET #EndDate = '2013-08-26'
DECLARE #BusinessDay TABLE
(
CalendarDate DATETIME,
IsBusinessDay INT
)
DECLARE #Counter DATETIME = #StartDate
WHILE(#Counter <= #EndDate)
BEGIN
INSERT INTO #WorkDays
SELECT #Counter, CASE WHEN DATENAME(WEEKDAY, #Counter) NOT IN ('Saturday', 'Sunday') THEN 1 ELSE 0 END
SET #Counter = DATEADD(DAY, 1, #Counter)
END
SELECT * FROM #BusinessDay
The downside is this has to be recreated for each query that needs it, so if you're doing this often, a fixed table might be a better way to go.
It can be used like this....
SELECT
BusinessDays = SUM(IsBusinessDay)
FROM
#BusinessDay
WHERE
CalendarDate BETWEEN #StartDate AND #EndDate
That will give you the count of business days between the two dates. Like many others have said, this obviously does not take into account any holidays or my birthday.

Based on previous code, I adapted it to exclude the last day (not asked but I needed it).
select (DATEDIFF(dd,#fromDate, #toDate))
- (DATEDIFF(ww,#fromDate, DATEADD(dd,-1,#toDate)) * 2)
- (CASE WHEN DATENAME(dw, #fromDate) = 'Sunday' THEN 1 else 0 end)
- (CASE WHEN DATENAME(dw, #toDate) = 'Sunday' THEN 1 else 0 end)
I removed the holydays by using a table containing those dates
- ( select count(distinct dcsdte)
from calendar_table
where dcsdte between #fromDate
and #toDate )

t-sql select get all Months within a range of years

I need a select to return Month and year Within a specified date range where I would input the start year and month and the select would return month and year from the date I input till today.
I know I can do this in a loop but I was wondering if it is possible to do this in a series selects?
Year Month
---- -----
2010 1
2010 2
2010 3
2010 4
2010 5
2010 6
2010 7
and so on.

Gosh folks... using a "counting recursive CTE" or "rCTE" is as bad or worse than using a loop. Please see the following article for why I say that.
http://www.sqlservercentral.com/articles/T-SQL/74118/
Here's one way to do it without any RBAR including the "hidden RBAR" of a counting rCTE.
--===== Declare and preset some obviously named variables
DECLARE #StartDate DATETIME,
#EndDate DATETIME
;
SELECT #StartDate = '2010-01-14', --We'll get the month for both of these
#EndDate = '2020-12-05' --dates and everything in between
;
WITH
cteDates AS
(--==== Creates a "Tally Table" structure for months to add to start date
-- calulated by the difference in months between the start and end date.
-- Then adds those numbers to the start of the month of the start date.
SELECT TOP (DATEDIFF(mm,#StartDate,#EndDate) + 1)
MonthDate = DATEADD(mm,DATEDIFF(mm,0,#StartDate)
+ (ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) -1),0)
FROM sys.all_columns ac1
CROSS JOIN sys.all_columns ac2
)
--===== Slice each "whole month" date into the desired display values.
SELECT [Year] = YEAR(MonthDate),
[Month] = MONTH(MonthDate)
FROM cteDates
;

I know this is an old question, but I'm mildly horrified at the complexity of some of the answers. Using a CTE is definitely the simplest way to go for selecting these values:
WITH months(dt) AS
(SELECT getdate() dt
UNION ALL
SELECT dateadd(month, -1, dt)
FROM months)
SELECT
top (datediff(month, '2017-07-01' /* start date */, getdate()) + 1)
YEAR(months.dt) yr, MONTH(months.dt) mnth
FROM months
OPTION (maxrecursion 0);
Just slap in whichever start date you'd like in place of the '2017-07-01' above and you're good to go with an efficient and easily-integrated solution.
Edit: Jeff Moden's answer quite effectively advocates against using rCTEs. However, in this case it appears to be a case of premature optimization - we're talking about 10's of records in all likelihood, and even if you span back to 1900 from today, it's still a minuscule hit. Using rCTEs to achieve code maintainability seems to be worth the trade if the expected result set is small.

You can use something like this: Link
To generate the equivalent of a numbers table using date ranges.
But could you please clarify your inputs and outputs?
Do you want to input a start date, for example, '2010-5-1' and end date, for example, '2010-8-1' and have it return every month between the two? Do you want to include the start month and end month, or exclude them?
Here's some code that I wrote that will quickly generate an inclusive result of every month between two dates.
--Inputs here:
DECLARE #StartDate datetime;
DECLARE #EndDate datetime;
SET #StartDate = '2010-1-5 5:00PM';
SET #EndDate = GETDATE();
--Procedure here:
WITH RecursiveRowGenerator (Row#, Iteration) AS (
SELECT 1, 1
UNION ALL
SELECT Row# + Iteration, Iteration * 2
FROM RecursiveRowGenerator
WHERE Iteration * 2 < CEILING(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1))
UNION ALL
SELECT Row# + (Iteration * 2), Iteration * 2
FROM RecursiveRowGenerator
WHERE Iteration * 2 < CEILING(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1))
)
, SqrtNRows AS (
SELECT *
FROM RecursiveRowGenerator
UNION ALL
SELECT 0, 0
)
SELECT TOP(DATEDIFF(MONTH, #StartDate, #EndDate)+1)
DATEADD(month, DATEDIFF(month, 0, #StartDate) + A.Row# * POWER(2,CEILING(LOG(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1))/LOG(2))) + B.Row#, 0) Row#
FROM SqrtNRows A, SqrtNRows B
ORDER BY A.Row#, B.Row#;

Code below generates the values for the range between 21 Jul 2013 and 15 Jan 2014.
I usually use it in SSRS reports for generating lookup values for the Month parameter.
declare
#from date = '20130721',
#to date = '20140115';
with m as (
select * from (values ('Jan', '01'), ('Feb', '02'),('Mar', '03'),('Apr', '04'),('May', '05'),('Jun', '06'),('Jul', '07'),('Aug', '08'),('Sep', '09'),('Oct', '10'),('Nov', '11'),('Dec', '12')) as t(v, c)),
y as (select cast(YEAR(getdate()) as nvarchar(4)) [v] union all select cast(YEAR(getdate())-1 as nvarchar(4)))
select m.v + ' ' + y.v [value_field], y.v + m.c [label_field]
from m
cross join y
where y.v + m.c between left(convert(nvarchar, #from, 112),6) and left(convert(nvarchar, #to, 112),6)
order by y.v + m.c desc
Results:
value_field label_field
---------------------------
Jan 2014 201401
Dec 2013 201312
Nov 2013 201311
Oct 2013 201310
Sep 2013 201309
Aug 2013 201308
Jul 2013 201307

you can do the following
SELECT DISTINCT YEAR(myDate) as [Year], MONTH(myDate) as [Month]
FROM myTable
WHERE <<appropriate criteria>>
ORDER BY [Year], [Month]

---Here is a version that gets the month end dates typically used for accounting purposes
DECLARE #StartDate datetime;
DECLARE #EndDate datetime;
SET #StartDate = '2010-1-1';
SET #EndDate = '2020-12-31';
--Procedure here:
WITH RecursiveRowGenerator (Row#, Iteration)
AS ( SELECT 1, 1
UNION ALL
SELECT Row# + Iteration, Iteration * 2
FROM RecursiveRowGenerator
WHERE Iteration * 2 < CEILING(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1))
UNION ALL SELECT Row# + (Iteration * 2), Iteration * 2
FROM RecursiveRowGenerator
WHERE Iteration * 2 < CEILING(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1)) )
, SqrtNRows AS ( SELECT * FROM RecursiveRowGenerator
UNION ALL SELECT 0, 0 )
SELECT TOP(DATEDIFF(MONTH, #StartDate, #EndDate)+1)
DateAdd(d,-1,DateAdd(m,1, DATEADD(month, DATEDIFF(month, 0, #StartDate) + A.Row# * POWER(2,CEILING(LOG(SQRT(DATEDIFF(MONTH, #StartDate, #EndDate)+1))/LOG(2))) + B.Row#, 0) ))
Row# FROM SqrtNRows A, SqrtNRows B ORDER BY A.Row#, B.Row#;

DECLARE #Date1 DATE
DECLARE #Date2 DATE
SET #Date1 = '20130401'
SET #Date2 = DATEADD(MONTH, 83, #Date1)
SELECT DATENAME(MONTH, #Date1) "Month", MONTH(#Date1) "Month Number", YEAR(#Date1) "Year"
INTO #Month
WHILE (#Date1 < #Date2)
BEGIN
SET #Date1 = DATEADD(MONTH, 1, #Date1)
INSERT INTO #Month
SELECT DATENAME(MONTH, #Date1) "Month", MONTH(#Date1) "Month Number", YEAR(#Date1) "Year"
END
SELECT * FROM #Month
ORDER BY [Year], [Month Number]
DROP TABLE #Month

declare #date1 datetime,
#date2 datetime,
#date datetime,
#month integer,
#nm_bulan varchar(20)
create table #month_tmp
( bulan integer null, keterangan varchar(20) null )
select #date1 = '2000-01-01',
#date2 = '2000-12-31'
select #month = month(#date1)
while (#month < 13)
Begin
IF #month = 1
Begin
SELECT #date = CAST( CONVERT(VARCHAR(25),DATEADD(dd,-(DAY(DATEADD(mm,0,#date1))-1),DATEADD(mm,0,#date1)),111) + ' 00:00:00' as DATETIME )
End
ELSE
Begin
SELECT #date = CAST( CONVERT(VARCHAR(25),DATEADD(dd,-(DAY(DATEADD(mm,#month -1,#date1))-1),DATEADD(mm,#month -1,#date1)),111) + ' 00:00:00' as DATETIME )
End
select #nm_bulan = DATENAME(MM, #date)
insert into #month_tmp
select #month as nilai, #nm_bulan as nama
select #month = #month + 1
End
select * from #month_tmp
drop table #month_tmp
go

Searching Week-wise/Month-wise record counts(number) and the StartDate+EndDate(datetime) of the Week/Month with Search between two Dates

I have a question in connection to this question earlier posted by me:-
Daily/Weekly/Monthly Record Count Search via StoredProcedure
I want to have the Count of Calls on Weekly-basis and Monthly-basis, Daily-basis issue is resolved.
ISSUE NUMBER #1:Weekly-basis Count of Calls and Start-Date and End-Date of Week
I have searched the Start-Date and End-Date of Week including their individual Count of Calls as well in the below-mentioned query. But the problem is that I could not get the result in one single table, although I have used the Temporary Tables(#TempTable+#TempTable2). Kindly help me in this regards.
NOTE:Table Creation commented as for executing more than once.
--CREATE TABLE #TempTable(StartDate datetime,EndDate datetime,CallCount numeric(18,5))
--CREATE TABLE #TempTable2(StartDate datetime,EndDate datetime,CallCount numeric(18,5))
DECLARE #StartDate datetime,#EndDate datetime,#StartDateTemp1 datetime,#StartDateTemp2 datetime,#EndDateTemp datetime,#Period varchar(50);
SET #StartDate='1/1/2010'; SET #EndDate='2/28/2010';
SET #StartDateTemp1=#StartDate; SET #StartDateTemp2=DATEADD(dd, 7, #StartDate );
SET #Period='Weekly';
IF (#Period = 'Weekly')
BEGIN
WHILE ((#StartDate <= #StartDateTemp1) AND (#StartDateTemp2 <= #EndDate))
BEGIN
IF((#StartDateTemp1 < #StartDateTemp2 ) AND (#StartDateTemp1 != #StartDateTemp2) )
BEGIN
SELECT
convert(varchar, #StartDateTemp1, 106) AS 'Start Date',
convert(varchar, #StartDateTemp2, 106) AS 'End Date',
COUNT(*) AS 'Call Count'
FROM TRN_Call
WHERE (CallTime >= #StartDateTemp1 AND CallTime <= #StartDateTemp2 );
END
SET #StartDateTemp1 = DATEADD(dd, 7, #StartDateTemp1);
SET #StartDateTemp2 = DATEADD(dd, 7, #StartDateTemp2);
END
END
ISSUE NUMBER #2:Monthly-basis Count of Calls and Start-Date and End-Date of Week
In this case, I have the same search, but will have to search the Call Counts plus the Start-Date and End-Date of the Month. Kindly help me in this regards as well.
DECLARE #StartDate datetime,#EndDate datetime,#StartDateTemp1 datetime,#StartDateTemp2 datetime,#EndDateTemp datetime,#Period varchar(50);
SET #StartDate='1/1/2010'; SET #EndDate='4/1/2010'; SET #StartDateTemp1=#StartDate;
--SET #StartDateTemp2=#StartDate;
SET #StartDateTemp2=DATEADD(mm, 1, #StartDate );
SET #Period='Monthly';
IF (#Period = 'Monthly')
BEGIN
WHILE ((#StartDate <= #StartDateTemp1) AND (#StartDateTemp2 <= #EndDate))
BEGIN
IF((#StartDateTemp1 < #StartDateTemp2 ) AND (#StartDateTemp1 != #StartDateTemp2) )
BEGIN
SELECT
convert(varchar, #StartDateTemp1, 106) AS 'Start Date',
convert(varchar, #StartDateTemp2, 106) AS 'End Date',
COUNT(*) AS 'Call Count'
FROM TRN_Call
WHERE (CallTime >= #StartDateTemp1 AND CallTime <= #StartDateTemp2 );
END
SET #StartDateTemp1 = DATEADD(mm, 1, #StartDateTemp1);
SET #StartDateTemp2 = DATEADD(mm, 1, #StartDateTemp2);
END
END

I believe following three simple queries suffice for what you need.
Daily
SELECT [Day] = CAST(CAST(CallTime AS INTEGER) AS DATETIME)
, [Call Count] = COUNT(*)
FROM TRN_Call
WHERE CallTime BETWEEN #StartDate AND #EndDate
GROUP BY CAST(CAST(CallTime AS INTEGER) AS DATETIME)
Weekly
SELECT [Week] = DATEPART(ww, CallTime)
, [Year] = DATEPART(yy, CallTime)
, [Call Count] = COUNT(*)
FROM TRN_Call
WHERE CallTime BETWEEN #StartDate AND #EndDate
GROUP BY DATEPART(ww, CallTime), DATEPART(yy, CallTime)
Monthly
SELECT [Month] = DATEPART(mm, CallTime)
, [Year] = DATEPART(yy, CallTime)
, [Call Count] = COUNT(*)
FROM TRN_Call
WHERE CallTime BETWEEN #StartDate AND #EndDate
GROUP BY DATEPART(mm, CallTime), DATEPART(yy, CallTime)

Simple query for find record month wise.....
SELECT invoice_no, created_at,month(created_at) month_no ,count(invoice_no) sale_count FROM sales_invoice WHERE company_id = ' .10 . ' AND status = "Approved" and year(created_at) = year(curdate()) group by month(created_at)enter code here

Calculating number of full months between two dates in SQL

I need to calculate the number of FULL month in SQL, i.e.
2009-04-16 to 2009-05-15 => 0 full month
2009-04-16 to 2009-05-16 => 1 full month
2009-04-16 to 2009-06-16 => 2 full months
I tried to use DATEDIFF, i.e.
SELECT DATEDIFF(MONTH, '2009-04-16', '2009-05-15')
but instead of giving me full months between the two date, it gives me the difference of the month part, i.e.
1
anyone know how to calculate the number of full months in SQL Server?

The original post had some bugs... so I re-wrote and packaged it as a UDF.
CREATE FUNCTION FullMonthsSeparation
(
#DateA DATETIME,
#DateB DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE #Result INT
DECLARE #DateX DATETIME
DECLARE #DateY DATETIME
IF(#DateA < #DateB)
BEGIN
SET #DateX = #DateA
SET #DateY = #DateB
END
ELSE
BEGIN
SET #DateX = #DateB
SET #DateY = #DateA
END
SET #Result = (
SELECT
CASE
WHEN DATEPART(DAY, #DateX) > DATEPART(DAY, #DateY)
THEN DATEDIFF(MONTH, #DateX, #DateY) - 1
ELSE DATEDIFF(MONTH, #DateX, #DateY)
END
)
RETURN #Result
END
GO
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-15') as MonthSep -- =0
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-16') as MonthSep -- =1
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-06-16') as MonthSep -- =2

select case when DATEPART(D,End_dATE) >=DATEPART(D,sTAR_dATE)
THEN ( case when DATEPART(M,End_dATE) = DATEPART(M,sTAR_dATE) AND DATEPART(YYYY,End_dATE) = DATEPART(YYYY,sTAR_dATE)
THEN 0 ELSE DATEDIFF(M,sTAR_dATE,End_dATE)END )
ELSE DATEDIFF(M,sTAR_dATE,End_dATE)-1 END

What's your definition of a month? Technically a month can be 28,29,30 or 31 days depending on the month and leap years.
It seems you're considering a month to be 30 days since in your example you disregarded that May has 31 days, so why not just do the following?
SELECT DATEDIFF(DAY, '2009-04-16', '2009-05-15')/30
, DATEDIFF(DAY, '2009-04-16', '2009-05-16')/30
, DATEDIFF(DAY, '2009-04-16', '2009-06-16')/30

The dateadd function can be used to offset to the beginning of the month. If the endDate has a day part less than startDate, it will get pushed to the previous month, thus datediff will give the correct number of months.
DATEDIFF(MONTH, DATEADD(DAY,-DAY(startDate)+1,startDate),DATEADD(DAY,-DAY(startDate)+1,endDate))

This is for ORACLE only and not for SQL-Server:
months_between(to_date ('2009/05/15', 'yyyy/mm/dd'),
to_date ('2009/04/16', 'yyyy/mm/dd'))
And for full month:
round(months_between(to_date ('2009/05/15', 'yyyy/mm/dd'),
to_date ('2009/04/16', 'yyyy/mm/dd')))
Can be used in Oracle 8i and above.

I know this is an old question, but as long as the dates are >= 01-Jan-1753 I use:
DATEDIFF(MONTH, DATEADD(DAY,-DAY(#Start)+1,#Start),DATEADD(DAY,-DAY(#Start)+1,#End))

DATEDIFF() is designed to return the number boundaries crossed between the two dates for the span specified. To get it to do what you want, you need to make an additional adjustment to account for when the dates cross a boundary but don't complete the full span.

WITH
-- Count how many months must be added to #StartDate to exceed #DueDate
MONTHS_SINCE(n, [Month_hence], [IsFull], [RemainingDays] ) AS (
SELECT
1 as n,
DATEADD(Day, -1, DATEADD(Month, 1, #StartDate)) AS Month_hence
,CASE WHEN (DATEADD(Day, -1, DATEADD(Month, 1, #StartDate)) <= #LastDueDate)
THEN 1
ELSE 0
END AS [IsFull]
,DATEDIFF(day, #StartDate, #LastDueDate) as [RemainingDays]
UNION ALL
SELECT
n+1,
--DateAdd(Month, 1, Month_hence) as Month_hence -- No, causes propagation of short month discounted days
DATEADD(Day, -1, DATEADD(Month, n+1, #StartDate)) as Month_hence
,CASE WHEN (DATEADD(Day, -1, DATEADD(Month, n+1, #StartDate)) <= #LastDueDate)
THEN 1
ELSE 0
END AS [IsFull]
,DATEDIFF(day, DATEADD(Day, -1, DATEADD(Month, n, #StartDate)), #LastDueDate)
FROM MONTHS_SINCE
WHERE Month_hence<( #LastDueDate --WHERE Period= 1
)
), --SELECT * FROM MONTHS_SINCE
MONTH_TALLY (full_months_over_all_terms, months_over_all_terms, days_in_incomplete_month ) AS (
SELECT
COALESCE((SELECT MAX(n) FROM MONTHS_SINCE WHERE isFull = 1),1) as full_months_over_all_terms,
(SELECT MAX(n) FROM MONTHS_SINCE ) as months_over_all_terms,
COALESCE((SELECT [RemainingDays] FROM MONTHS_SINCE WHERE isFull = 0),0) as days_in_incomplete_month
) SELECT * FROM MONTH_TALLY;

Is not necesary to create the function only the #result part. For example:
Select Name,
(SELECT CASE WHEN
DATEPART(DAY, '2016-08-28') > DATEPART(DAY, '2016-09-29')
THEN DATEDIFF(MONTH, '2016-08-28', '2016-09-29') - 1
ELSE DATEDIFF(MONTH, '2016-08-28', '2016-09-29') END) as NumberOfMonths
FROM
tableExample;

This answer follows T-SQL format. I conceptualize this problem as one of a linear-time distance between two date points in datetime format, call them Time1 and Time2; Time1 should be aligned to the 'older in time' value you are dealing with (say a Birth date or a widget Creation date or a journey Start date) and Time2 should be aligned with the 'newer in time' value (say a snapshot date or a widget completion date or a journey checkpoint-reached date).
DECLARE #Time1 DATETIME
SET #Time1 = '12/14/2015'
DECLARE #Time2 DATETIME
SET #Time2 = '12/15/2016'
The solution leverages simple measurement, conversion and calculations of the serial intersections of multiple cycles of different lengths; here: Century,Decade,Year,Month,Day (Thanks Mayan Calendar for the concept!). A quick note of thanks: I thank other contributors to Stack Overflow for showing me some of the component functions in this process that I've stitched together. I've positively rated these in my time on this forum.
First, construct a horizon that is the linear set of the intersections of the Century,Decade,Year,Month cycles, incremental by month. Use the cross join Cartesian function for this. (Think of this as creating the cloth from which we will cut a length between two 'yyyy-mm' points in order to measure distance):
SELECT
Linear_YearMonths = (centuries.century + decades.decade + years.[year] + months.[Month]),
1 AS value
INTO #linear_months
FROM
(SELECT '18' [century] UNION ALL
SELECT '19' UNION ALL
SELECT '20') centuries
CROSS JOIN
(SELECT '0' [decade] 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') decades
CROSS JOIN
(SELECT '1' [year] 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 '0') years
CROSS JOIN
(SELECT '-01' [month] UNION ALL
SELECT '-02' UNION ALL
SELECT '-03' UNION ALL
SELECT '-04' UNION ALL
SELECT '-05' UNION ALL
SELECT '-06' UNION ALL
SELECT '-07' UNION ALL
SELECT '-08' UNION ALL
SELECT '-09' UNION ALL
SELECT '-10' UNION ALL
SELECT '-11' UNION ALL
SELECT '-12') [months]
ORDER BY 1
Then, convert your Time1 and Time2 date points into the 'yyyy-mm' format (Think of these as the coordinate cut points on the whole cloth). Retain the original datetime versions of the points as well:
SELECT
Time1 = #Time1,
[YYYY-MM of Time1] = CASE
WHEN LEFT(MONTH(#Time1),1) <> '1' OR MONTH(#Time1) = '1'
THEN (CAST(YEAR(#Time1) AS VARCHAR) + '-' + '0' + CAST(MONTH(#Time1) AS VARCHAR))
ELSE (CAST(YEAR(#Time1) AS VARCHAR) + '-' + CAST(MONTH(#Time1) AS VARCHAR))
END,
Time2 = #Time2,
[YYYY-MM of Time2] = CASE
WHEN LEFT(MONTH(#Time2),1) <> '1' OR MONTH(#Time2) = '1'
THEN (CAST(YEAR(#Time2) AS VARCHAR) + '-' + '0' + CAST(MONTH(#Time2) AS VARCHAR))
ELSE (CAST(YEAR(#Time2) AS VARCHAR) + '-' + CAST(MONTH(#Time2) AS VARCHAR))
END
INTO #datepoints
Then, Select the ordinal distance of 'yyyy-mm' units, less one to convert to cardinal distance (i.e. cut a piece of cloth from the whole cloth at the identified cut points and get its raw measurement):
SELECT
d.*,
Months_Between = (SELECT (SUM(l.value) - 1) FROM #linear_months l
WHERE l.[Linear_YearMonths] BETWEEN d.[YYYY-MM of Time1] AND d.[YYYY-MM of Time2])
FROM #datepoints d
Raw Output:
I call this a 'raw distance' because the month component of the 'yyyy-mm' cardinal distance may be one too many; the day cycle components within the month need to be compared to see if this last month value should count. In this example specifically, the raw output distance is '12'. But this wrong as 12/14 is before 12/15, so therefore only 11 full months have lapsed--its just one day shy of lapsing through the 12th month. We therefore have to bring in the intra-month day cycle to get to a final answer. Insert a 'month,day' position comparison between the to determine if the latest date point month counts nominally, or not:
SELECT
d.*,
Months_Between = (SELECT (SUM(l.value) - 1) FROM AZ_VBP.[MY].[edg_Linear_YearMonths] l
WHERE l.[Linear_YearMonths] BETWEEN d.[YYYY-MM of Time1] AND d.[YYYY-MM of Time2])
+ (CASE WHEN DAY(Time1) < DAY(Time2)
THEN -1
ELSE 0
END)
FROM #datepoints d
Final Output:
The correct answer of '11' is now our output. And so, I hope this helps. Thanks!

select CAST(DATEDIFF(MONTH, StartDate, EndDate) AS float) -
(DATEPART(dd,StartDate) - 1.0) / DATEDIFF(DAY, StartDate, DATEADD(MONTH, 1, StartDate)) +
(DATEPART(dd,EndDate)*1.0 ) / DATEDIFF(DAY, EndDate, DATEADD(MONTH, 1, EndDate))

I realize this is an old post, but I created this interesting solution that I think is easy to implement using a CASE statement.
Estimate the difference using DATEDIFF, and then test the months before and after using DATEADD to find the best date. This assumes Jan 31 to Feb 28 is 1 month (because it is).
DECLARE #First date = '2015-08-31'
DECLARE #Last date = '2016-02-28'
SELECT
#First as [First],
#Last as [Last],
DateDiff(Month, #First, #Last) as [DateDiff Thinks],
CASE
WHEN DATEADD(Month, DATEDIFF(Month, #First, #Last) +1, #First) <= #Last Then DATEDIFF(Month, #First, #Last) +1
WHEN DATEADD(Month, DATEDIFF(Month, #First, #Last) , #First) <= #Last Then DATEDIFF(Month, #First, #Last)
WHEN DATEADD(Month, DATEDIFF(Month, #First, #Last) -1, #First) <= #Last Then DATEDIFF(Month, #First, #Last) -1
END as [Actual Months Apart]

SIMPLE AND EASY WAY, Just Copy and Paste this FULL code to MS SQL and Execute :
declare #StartDate date='2019-01-31'
declare #EndDate date='2019-02-28'
SELECT
DATEDIFF(MONTH, #StartDate, #EndDate)+
(
case
when format(#StartDate,'yyyy-MM') != format(#EndDate,'yyyy-MM') AND DATEPART(DAY,#StartDate) > DATEPART(DAY,#EndDate) AND DATEPART(DAY,#EndDate) = DATEPART(DAY,EOMONTH(#EndDate)) then 0
when format(#StartDate,'yyyy-MM') != format(#EndDate,'yyyy-MM') AND DATEPART(DAY,#StartDate) > DATEPART(DAY,#EndDate) then -1
else 0
end
)
as NumberOfMonths

All you need to do is deduct the additional month if the end date has not yet passed the day of the month in the start date.
DECLARE #StartDate AS DATE = '2019-07-17'
DECLARE #EndDate AS DATE = '2019-09-15'
DECLARE #MonthDiff AS INT = DATEDIFF(MONTH,#StartDate,#EndDate)
SELECT #MonthDiff -
CASE
WHEN FORMAT(#StartDate,'dd') > FORMAT(#EndDate,'dd') THEN 1
ELSE 0
END

You can create this function to calculate absolute difference between two dates.
As I found using DATEDIFF inbuilt system function we will get the difference only in months, days and years. For example : Let say there are two dates 18-Jan-2018 and 15-Jan-2019. So the difference between those dates will be given by DATEDIFF in month as 12 months where as it is actually 11 Months 28 Days. So using the function given below, we can find absolute difference between two dates.
CREATE FUNCTION GetDurationInMonthAndDays(#First_Date DateTime,#Second_Date DateTime)
RETURNS VARCHAR(500)
AS
BEGIN
DECLARE #RESULT VARCHAR(500)=''
DECLARE #MONTHS TABLE(MONTH_ID INT,MONTH_NAME VARCHAR(100),MONTH_DAYS INT)
INSERT INTO #MONTHS
SELECT 1,'Jan',31
union SELECT 2,'Feb',28
union SELECT 3,'Mar',31
union SELECT 4,'Apr',30
union SELECT 5,'May',31
union SELECT 6,'Jun',30
union SELECT 7,'Jul',31
union SELECT 8,'Aug',31
union SELECT 9,'Sep',30
union SELECT 10,'Oct',31
union SELECT 11,'Nov',30
union SELECT 12,'Jan',31
IF(#Second_Date>#First_Date)
BEGIN
declare #month int=0
declare #days int=0
declare #first_year int
declare #second_year int
SELECT #first_year=Year(#First_Date)
SELECT #second_year=Year(#Second_Date)+1
declare #first_month int
declare #second_month int
SELECT #first_month=Month(#First_Date)
SELECT #second_month=Month(#Second_Date)
if(#first_month=2)
begin
IF((#first_year%100<>0) AND (#first_year%4=0) OR (#first_year%400=0))
BEGIN
SELECT #days=29-day(#First_Date)
END
else
begin
SELECT #days=28-day(#First_Date)
end
end
else
begin
SELECT #days=(SELECT MONTH_DAYS FROM #MONTHS WHERE MONTH_ID=#first_month)-day(#First_Date)
end
SELECT #first_month=#first_month+1
WHILE #first_year<#second_year
BEGIN
if(#first_month=13)
begin
set #first_month=1
end
WHILE #first_month<13
BEGIN
if(#first_year=Year(#Second_Date))
begin
if(#first_month=#second_month)
begin
SELECT #days=#days+DAY(#Second_Date)
break;
end
else
begin
SELECT #month=#month+1
end
end
ELSE
BEGIN
SELECT #month=#month+1
END
SET #first_month=#first_month+1
END
SET #first_year = #first_year + 1
END
select #month=#month+(#days/30)
select #days=#days%30
if(#days>0)
begin
SELECT #RESULT=CAST(#month AS VARCHAR)+' Month '+CAST(#days AS VARCHAR)+' Days '
end
else
begin
SELECT #RESULT=CAST(#month AS VARCHAR)+' Month '
end
END
ELSE
BEGIN
SELECT #RESULT='ERROR'
END
RETURN #RESULT
END

SELECT dateadd(dd,number,DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)) AS gun FROM master..spt_values
WHERE type = 'p'
AND year(dateadd(dd,number,DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)))=year(DATEADD(yy, DATEDIFF(yy,0,getdate()), 0))

CREATE FUNCTION ufFullMonthDif (#dStart DATE, #dEnd DATE)
RETURNS INT
AS
BEGIN
DECLARE #dif INT,
#dEnd2 DATE
SET #dif = DATEDIFF(MONTH, #dStart, #dEnd)
SET #dEnd2 = DATEADD (MONTH, #dif, #dStart)
IF #dEnd2 > #dEnd
SET #dif = #dif - 1
RETURN #dif
END
GO
SELECT dbo.ufFullMonthDif ('2009-04-30', '2009-05-01')
SELECT dbo.ufFullMonthDif ('2009-04-30', '2009-05-29')
SELECT dbo.ufFullMonthDif ('2009-04-30', '2009-05-30')
SELECT dbo.ufFullMonthDif ('2009-04-16', '2009-05-15')
SELECT dbo.ufFullMonthDif ('2009-04-16', '2009-05-16')
SELECT dbo.ufFullMonthDif ('2009-04-16', '2009-06-16')
SELECT dbo.ufFullMonthDif ('2019-01-31', '2019-02-28')

Making Some changes to the Above function worked for me.
CREATE FUNCTION [dbo].[FullMonthsSeparation]
(
#DateA DATETIME,
#DateB DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE #Result INT
DECLARE #DateX DATETIME
DECLARE #DateY DATETIME
IF(#DateA < #DateB)
BEGIN
SET #DateX = #DateA
SET #DateY = #DateB
END
ELSE
BEGIN
SET #DateX = #DateB
SET #DateY = #DateA
END
SET #Result = (
SELECT
CASE
WHEN DATEPART(DAY, #DateX) > DATEPART(DAY, #DateY)
THEN DATEDIFF(MONTH, #DateX, #DateY) - iif(EOMONTH(#DateY) = #DateY, 0, 1)
ELSE DATEDIFF(MONTH, #DateX, #DateY)
END
)
RETURN #Result
END

Declare #FromDate datetime, #ToDate datetime,
#TotalMonth int ='2021-10-01', #TotalDay='2021-12-31' int,
#Month int = 0
WHILE #ToDate > DATEADD(MONTH,#Month,#FromDate)
BEGIN
SET #Month = #Month +1
END
SET #TotalMonth = #Month -1
SET #TotalDay = DATEDIFF(DAY, DATEADD(MONTH,#TotalMonth, #FromDate),#ToDate) +1
IF(#TotalDay = DAY(EOMONTH(#ToDate)))
BEGIN
SET #TotalMonth = #TotalMonth +1
SET #TotalDay =0
END
Result #TotalMonth = 3, #TotalDay=0

if you are using PostGres only --
SELECT (DATE_PART('year', '2012-01-01'::date) - DATE_PART('year', '2011-10-02'::date)) * 12 +
(DATE_PART('month', '2012-01-01'::date) - DATE_PART('month', '2011-10-02'::date));

There are a lot of answers here that did not satisfy all the corner cases so I set about to fix them. This handles:
01/05/2021 - 02/04/2021 = 0 months
01/31/2021 - 02/28/2021 = 1 months
09/01/2021 - 10/31/2021 = 2 months
I think this generally handles all the cases needed.
declare #dateX date = '01/1/2022'
declare #datey date = '02/28/2022'
-- select datediff(month, #dateX, #datey) --Here for comparison
SELECT
CASE
WHEN DATEPART(DAY, #DateX) = 1 and DATEPART(DAY, #DateY) = DATEPART(DAY, eomonth(#DateY))
THEN DATEDIFF(MONTH, #DateX, #DateY) + 1
WHEN DATEPART(DAY, #DateX) > DATEPART(DAY, #DateY) and DATEPART(DAY, #DateY) != DATEPART(DAY, eomonth(#DateY))
THEN DATEDIFF(MONTH, #DateX, #DateY) - 1
ELSE DATEDIFF(MONTH, #DateX, #DateY)
END

I believe it is important to note that the question specifically asks for "full months between" AND that in the examples given each date is treated as "the START point of that date". This latter item is important because some comments state that year-01-31 to year-02-28 is a result of zero. This is correct. 1 complete day in January, plus 27 complete days in February (02-28 is the start of that day, so incomplete) is zero "full" months.
With that in mind I believe the following would meet the requirements IF StartDate is <= EndDate
(DATEPART(YEAR, EndDate) - DATEPART(YEAR, StartDate)) * 12
+ (DATEPART(MONTH, EndDate) - DATEPART(MONTH, StartDate))
- CASE WHEN DATEPART(DAY,EndDate) < DATEPART(DAY,StartDate) THEN 1 ELSE 0 END
To accommodate the possibility that the dates may be in any order then:
, CASE WHEN StartDate <= EndDate THEN
(DATEPART(YEAR, EndDate) - DATEPART(YEAR, StartDate)) * 12
+ (DATEPART(MONTH, EndDate) - DATEPART(MONTH, StartDate))
- CASE WHEN DATEPART(DAY,EndDate) < DATEPART(DAY,StartDate) THEN 1 ELSE 0 END
ELSE
(DATEPART(YEAR, StartDate) - DATEPART(YEAR, EndDate)) * 12
+ (DATEPART(MONTH, StartDate) - DATEPART(MONTH, EndDate))
- CASE WHEN DATEPART(DAY,StartDate) < DATEPART(DAY,EndDate) THEN 1 ELSE 0 END
END AS FullMnthsBtwn
For this sample:
select
StartDate, EndDate
into mytable
from (
values
(cast(getdate() as date),cast(getdate() as date)) -- both same date
-- original
,('2009-04-16','2009-05-15') -- > 0 full month
,('2009-04-16','2009-05-16') -- > 1 full month
,('2009-04-16','2009-06-16') -- > 2 full months
-- '1/31/2018' and endDate of '3/1/2018', I get a 0 – Eugene
, ('2018-01-31','2018-03-01')
-- some extras mentioned in comments, both of these should return 0 (in my opinion)
,('2009-01-31','2009-02-28')
,('2012-12-31','2013-02-28')
,('2022-05-15','2022-04-16') -- > 0 full month
,('2022-05-16','2022-04-16') -- > 1 full month
,('2021-06-16','2022-04-16') -- > 10 full months
) d (StartDate, EndDate)
query
select
StartDate
, EndDate
, CASE WHEN StartDate <= EndDate THEN
(DATEPART(YEAR, EndDate) - DATEPART(YEAR, StartDate)) * 12
+ (DATEPART(MONTH, EndDate) - DATEPART(MONTH, StartDate))
- CASE WHEN DATEPART(DAY,EndDate) < DATEPART(DAY,StartDate) THEN 1 ELSE 0 END
ELSE
(DATEPART(YEAR, StartDate) - DATEPART(YEAR, EndDate)) * 12
+ (DATEPART(MONTH, StartDate) - DATEPART(MONTH, EndDate))
- CASE WHEN DATEPART(DAY,StartDate) < DATEPART(DAY,EndDate) THEN 1 ELSE 0 END
END AS FullMnthsBtwn
from mytable
order by 1
result
+------------+------------+---------------+
| StartDate | EndDate | FullMnthsBtwn |
+------------+------------+---------------+
| 2009-01-31 | 2009-02-28 | 0 |
| 2009-04-16 | 2009-05-15 | 0 |
| 2009-04-16 | 2009-05-16 | 1 |
| 2009-04-16 | 2009-06-16 | 2 |
| 2012-12-31 | 2013-02-28 | 1 |
| 2018-01-31 | 2018-03-01 | 1 |
| 2021-06-16 | 2022-04-16 | 10 |
| 2022-05-15 | 2022-04-16 | 0 |
| 2022-05-16 | 2022-04-16 | 1 |
| 2022-07-09 | 2022-07-09 | 0 |
+------------+------------+---------------+
See db<>fiddle here (compares some other responses as well)

I got some ideas from the other answers, but none of them gave me exactly what I wanted.
The problem boils down to what I perceive a "month between" to be, which may be what others are also looking for also.
For example 25th February to 25th March would be one month to me, even though it is only 28 days. I would also consider 25th March to 25th April as one month at 31 days.
Also, I would consider 31st January to 2nd March as 1 month and 2 days even though it is 30 days between.
Also, fractions of a month are a bit meaningless as it depends on the length of a month and which month in the range do you choose to take a fraction of.
So, with that in mind, I came up with this function. It returns a decimal, the integer part is the number of months and the decimal part is the number of days, so a return value of 3.07 would mean 3 months and 7 days.
CREATE FUNCTION MonthsAndDaysBetween (#fromDt date, #toDt date)
RETURNS decimal(10,2)
AS
BEGIN
DECLARE #d1 date, #d2 date, #numM int, #numD int, #trc varchar(10);
IF(#fromDt < #toDt)
BEGIN
SET #d1 = #fromDt;
SET #d2 = #toDt;
END
ELSE
BEGIN
SET #d1 = #toDt;
SET #d2 = #fromDt;
END
IF DAY(#d1)>DAY(#d2)
SET #numM = year(#d2)*12+month(#d2)-year(#d1)*12-month(#d1)-1;
ELSE
SET #numM = year(#d2)*12+month(#d2)-year(#d1)*12-month(#d1);
IF YEAR(#d1) < YEAR(#d2) OR (YEAR(#d1) = YEAR(#d2) AND MONTH(#d1) < MONTH(#d2))
BEGIN
IF DAY(#d2) < DAY(#d1)
SET #numD = DAY(#d2) + DAY(EOMONTH(DATEADD(month,-1,#d2))) - DAY(#d1);
ELSE
SET #numD = DAY(#d2)-DAY(#d1);
END
ELSE
SET #numD = DAY(#d2)-DAY(#d1);
RETURN #numM + ABS(#numD) / 100.0;
END

In sql server, this formula works for going backward and forward in time.
DATEDIFF(month,#startdate, #enddate) + iif(#startdate <=#enddate,IIF(DAY(#startdate) > DAY(#enddate),-1,0),IIF(DAY(#startdate) < DAY(#enddate),+1, 0)))

SELECT 12 * (YEAR(end_date) - YEAR(start_date)) +
((MONTH(end_date) - MONTH(start_date))) +
SIGN(DAY(end_date) / DAY(start_date));
This works fine for me on SQL SERVER 2000.

Try:
trunc(Months_Between(date2, date1))

UPDATED
Right now, I just use
SELECT DATEDIFF(MONTH, '2019-01-31', '2019-02-28')
and SQL server returns the exact result (1).

I googled over internet.
And suggestion I found is to add +1 to the end.
Try do it like this:
Declare #Start DateTime
Declare #End DateTime
Set #Start = '11/1/07'
Set #End = '2/29/08'
Select DateDiff(Month, #Start, #End + 1)