PostgreSQL Table joins

with icu_cohort as (
Select ie.subject_id, ie.hadm_id, ie.stay_id
-- hospital level factors
, adm.admittime, adm.dischtime, adm.race, adm.deathtime
, adm.hospital_expire_flag
, DENSE_RANK() OVER (PARTITION BY adm.subject_id ORDER BY adm.admittime) AS hospstay_seq
, CASE
    WHEN DENSE_RANK() OVER (PARTITION BY adm.subject_id ORDER BY adm.admittime) = 1 THEN True
    ELSE False END AS first_hosp_stay	
-- icu level factors 
, ie.intime as icu_intime, ie.outtime as icu_outtime
, (ie.outtime -  ie.intime) as los_icu
, DENSE_RANK() OVER (PARTITION BY ie.hadm_id ORDER BY ie.intime) AS icustay_seq
-- first ICU stay for the current hospitalization
, CASE
    WHEN DENSE_RANK() OVER (PARTITION BY ie.hadm_id ORDER BY ie.intime) = 1 THEN True
    ELSE False END AS first_icu_stay,
-- patients info 
	pa.gender, pa.anchor_age, pa.dod
	
FROM mimiciv_icu.icustays as ie
Left JOIN  mimiciv_hosp.admissions as adm
    ON ie.hadm_id = adm.hadm_id
Left JOIN  mimiciv_hosp.patients as pa
	on ie.subject_id = pa.subject_id
),
	
lab_info as (
Select valuenum, valueuom, subject_id, itemid, charttime, storetime 
from mimiciv_hosp.labevents
where itemid = 51002 OR itemid = 51003 OR itemid = 52642 OR itemid = 51222 and valuenum is not null
)

-- select count (distinct icu_cohort.subject_id)
select *
from icu_cohort
left join lab_info
on icu_cohort.subject_id = lab_info.subject_id
where first_icu_stay = 'True' and  first_hosp_stay = 'True' and lab_info.valuenum is not null