How to break up a date range in sql by months

Question

I have two sql tables. they are for employees at a company. one table has the usual details (id,name,surname) and another table has their leave info (empid *foreign key to id in employee table,datefrom,dateto)

I needed to break down the leave structure so that we can display the dates. in an output, we would have : DateFrom DateT 18-01-2013 19-01-2013

now if the employee has taken leave that goes over the month (ie, it goes from the 29 to the 5), I would print the values like so: DateFrom DateT 29-01-2013 31-01-2013 01-02-2013 05-02-2013

to print this, I used breaking up a date range by month which helped break it down, thanks for that answer. but how do I display which employee is getting all that leave? as I said, the tables are linked. I tried using

select
    e.Firstname,
    e.Surname,
    e.MobileNum,
    convert(varchar(11),case when DateFrom > MonthStart then DateFrom else MonthStart end) as BeginDate,
    convert(varchar(11),case when DateTo < MonthEnd then DateTo else MonthEnd end) as EndDate

from(
    select l.*,
    (
        dateadd(month,datediff(month,0,l.datefrom)+v.number,0)
    ) as MonthStart,
    DATEADD(day,-1,
        dateadd(month,datediff(month,0,l.datefrom)+v.number+1,0)
    ) as MonthEnd

from EmployeeLeave l, Employees E
     inner join master..spt_values v on v.type='P' 
     and v.number between 0 and DATEDIFF(month,l.datefrom,l.dateto)
) s 

but I get errors saying, multipart identifier could not be bound. and I can't find a spot to say

where l.empid = e.empid

so could someone please tell me how to fix this. would like to see the employee that is taking leave off

Answer 1

You join EmployeeLeave and Employees here:

from EmployeeLeave l inner join Employees E
on l.empid = e.id
 inner join master..spt_values v on v.type='P' 
 and v.number between 0 and DATEDIFF(month,l.datefrom,l.dateto)

You select the fields from Employees here:

from(
select l.*, e.FirstName, e.Surname, e,MobileNum
(
    dateadd(month,datediff(month,0,l.datefrom)+v.number,0)
) as MonthStart,  etc

Then, change this:

select e.Firstname, e.Surname, e.MobileNum

to this

select s.Firstname, s.Surname, s.MobileNum

The reason is that you are selecting from a derived table named s, not the actual employees table.