Question : SQL Select Date from multiple fields if not null

I am extracting data from multiple tables on SQL Server. I have everything I need except 1 field. My query results needs to date fields, call then start and end - in the joined tables I have fields

d1,d2,d3,d4,d5 -   where d5  is the end date and always populated. dates d1-d4 are related to a progression toward d5 and may or may not be null. If they are all nul then start and end are both equal to d5, otherwise from d4 ---> d1 start is the first field that has a date in it.  I need something like

Select iif( is not null(d4,d4,iif(is not null(d3,d3,iif(is not null(d2,d2,iif(is not null(d1,d1,d5))))) AS start, d5 AS end.....

but in Transact-SQL

Hope this makes sense

Stan

Answer : SQL Select Date from multiple fields if not null

select coalesce(d4,d3,d2,d1, d5) start_date, d5 as end_date