Oracle 11g Release 2

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with table1(Employee_Name, Employee_ID, Team_Leader, Location, Start_Date, End_Date) as (
    select 'John Smith', '123123', 'Team A', 'Site A', date '2019-01-01', date '2019-01-01' from dual union all
    select 'John Smith', '123123', 'Team A', 'Site A', date '2019-01-02', date '2019-01-03' from dual union all
    select 'John Smith', '123123', 'Team B', 'Site A', date '2019-01-03', date '2019-01-04' from dual union all
    select 'John Smith', '123123', 'Team A', 'Site A', date '2019-01-04', date '2019-01-05' from dual union all
    select 'John Smith', '123123', 'Team B', 'Site A', date '2019-01-05', date '2019-01-06' from dual )
select Employee_Name, Employee_ID, Team_Leader, Location, min(Start_Date) sdt, max(End_Date) edt
  from (
  select t.*, sum(change) over (partition by employee_id order by start_date) grp
    from (
      select t.*, 
             case when team_leader 
                     = lag(team_leader) over (partition by employee_id order by start_date) 
                   and location 
                     = lag(location) over (partition by employee_id order by start_date) 
                  then 0 
                  else 1 
             end change
        from table1 t) t)
  group by Employee_Name, Employee_ID, Team_Leader, Location, grp
  order by employee_id, min(start_date)

EMPLOYEE_NAME	EMPLOYEE_ID	TEAM_LEADER	LOCATION	SDT	EDT
John Smith	123123	Team A	Site A	01-JAN-19	03-JAN-19
John Smith	123123	Team B	Site A	03-JAN-19	04-JAN-19
John Smith	123123	Team A	Site A	04-JAN-19	05-JAN-19
John Smith	123123	Team B	Site A	05-JAN-19	06-JAN-19