use Leo
go

alter proc dbo.proc_UpdateHolidaysTable
as
if not exists(select TABLE_NAME from INFORMATION_SCHEMA.TABLES where TABLE_NAME = 'HOLIDAYS')
  create table dbo.HOLIDAYS(dt date primary key clustered, Holiday varchar(50))

declare @year int = 2019

while @year < year(getdate()) + 40
begin
  insert into dbo.Holidays(dt, Holiday)
  select fhol.dt, fhol.Holiday
  from
    dbo.tvf_GetHolidays(@year) fhol
    left join dbo.Holidays tbh on fhol.dt = tbh.dt
  where fhol.dt is null

  set @year = @year + 1
end
go