Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE repair_assignment ( technician_id number, repair_id number, machine_id number )
TABLE: CREATE TABLE machine ( machine_id number, making_year number, class text, team text, machine_series text, value_points number, quality_rank number )
TABLE: CREATE TABLE repair ( repair_id number, name text, launch_date text, notes text )
TABLE: CREATE TABLE technician ( technician_id number, name text, team text, starting_year number, age number )

### Question ###
Show the starting years shared by technicians from team 'CLE' and 'CWS'.

### Accurate SQL ###

SELECT starting_year FROM technician WHERE team = "CLE" INTERSECT SELECT starting_year FROM technician WHERE team = "CWS"