CREATE TABLE prescriptions (subject_id CLOB, hadm_id CLOB, icustay_id CLOB, drug_type CLOB, drug CLOB, formulary_drug_cd CLOB, route CLOB, drug_dose CLOB)
CREATE TABLE lab (subject_id CLOB, hadm_id CLOB, itemid CLOB, charttime CLOB, flag CLOB, value_unit CLOB, label CLOB, fluid CLOB)
CREATE TABLE demographic (subject_id CLOB, hadm_id CLOB, name CLOB, marital_status CLOB, age CLOB, dob CLOB, gender CLOB, language CLOB, religion CLOB, admission_type CLOB, days_stay CLOB, insurance CLOB, ethnicity CLOB, expire_flag CLOB, admission_location CLOB, discharge_location CLOB, diagnosis CLOB, dod CLOB, dob_year CLOB, dod_year CLOB, admittime CLOB, dischtime CLOB, admityear CLOB)
CREATE TABLE procedures (subject_id CLOB, hadm_id CLOB, icd9_code CLOB, short_title CLOB, long_title CLOB)
CREATE TABLE diagnoses (subject_id CLOB, hadm_id CLOB, icd9_code CLOB, short_title CLOB, long_title CLOB)

give me the number of patients whose diagnoses icd9 code is 44020 and lab test category is hematology?
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.icd9_code = "44020" AND lab."CATEGORY" = "Hematology"
SELECT COUNT(DISTINCT "demographic"."subject_id") FROM "demographic" JOIN "diagnoses" ON "44020" = "diagnoses"."icd9_code" AND "demographic"."hadm_id" = "diagnoses"."hadm_id" JOIN "lab" ON "Hematology" = "lab"."CATEGORY" AND "demographic"."hadm_id" = "lab"."hadm_id"