PostgreSQL Select value row depending on another value row

Question

How to select only the value of the column phase that corresponds to the value of the column type?, that way I want to show only the TAXI_SMALL values if the value of type is small_airport, or TAXI_LARGE If the value of type is large_airport as in a sample of my table:

ident	type	aircraft	phase	co2_lto_kg
LFPG	large_airport	AC300	APPROACH	2033.64
LFPG	large_airport	AC300	CLIMB OUT	3279.83
LFPG	large_airport	AC300	TAKE OFF	1281.1932
LFPG	large_airport	AC300	TAXI_LARGE	3675.672
LFPG	large_airport	AC300	TAXI_MEDIUM	2261.952
LFPG	large_airport	AC300	TAXI_SMALL	1413.72

The desired result:

ident	type	aircraft	phase	co2_lto_kg
LFPG	large_airport	AC300	APPROACH	2033.64
LFPG	large_airport	AC300	CLIMB OUT	3279.83
LFPG	large_airport	AC300	TAKE OFF	1281.1932
LFPG	large_airport	AC300	TAXI_LARGE	3675.672

This is the code I've so far and I know that the CASE instance is not at all right...

select 
ident, type, aircraft, phase,
avg(co2_by_phase_lto) as co2_lto_kg,
case(
    WHEN t.type ilike 'large'||'%' THEN phase('TAXI_LARGE')
)
from aviation.emissionsco2 as t
where t.aircraft ilike '%'||'300' and
t.rep_airp ilike '%'||'lfpg'
group by ident,phase

Answer 1

You can use NOT LIKE to include all the non taxi related data -- check that the phase doesn't begin with TAXI_. Then add for each size a comparison that couples the airport size to the taxi route with OR.

SELECT *
       FROM aviation.emissionsco2
       WHERE phase NOT LIKE 'TAXI$_%' ESCAPE '$'
              OR (phase,
                  type) IN (('TAXI_LARGE',
                             'large_airport'),
                            ('TAXI_MEDIUM',
                             'medium_airport'),
                            ('TAXI_SMALL',
                             'small_airport'));