Split a single row into multiple rows based on date range in sql server

Question

my SQL server table structure is some what like below

FROM_Currency   To_Currency   ExchangeRate   StartDate    EndDate
EUR               GBP            33.5        2018-03-31    2018-04-30
USD               EUR            22.9        2019-01-31    2019-02-28

like this have historical exchange rate data for multiple currencies and exchange rate for over 3 years, as shown in above table we have start date and enddate for each currency rate in a range of 1 month,what i need is to basically split it into each day,so basically need exchange rate daily,for ex: for 1st record i need 30 rows which should say from_currency as EUR and To_currency as GBP and exchange rate as 33.5 and new date column should be increment date starting from 2018-03-31 to 2018-04-30.

Answer 1

One option uses a recursive query:

with cte as (
    select 
         from_currency, 
         to_currency, 
         exchange_rage, 
         startDate, 
         endDate, 
         startDate currentDate
    from mytable t
    union all
    select 
         from_currency, 
         to_currency, 
         exchange_rage, 
         startDate, 
         endDate, 
         dateadd(day, 1, currentDate)
    from cte
    where currentDate < endDate
)
select from_currency, to_currency, exchange_rage, currentDate from cte

If your any of your periods span over more 100 days, then you need to add option(maxrecursion 0) at the end of the query.