MySQL 8.0

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CREATE TABLE patient_table
    (`patient_id` varchar(5), `disease` varchar(8))
;
    
INSERT INTO patient_table
    (`patient_id`, `disease`)
VALUES
    ('hashA', 'HIV-2'),
    ('hashA', 'COPD-1'),
    ('hashA', 'diabetes'),
    ('hashB', 'diabetes'),
    ('hashB', 'FSGS')
;
select t.*
from patient_table t
   where exists (select 1
      from patient_table t2
      where t2.disease like '%diabetes%'  and
            t.patient_id = t2.patient_id
)
AND NOT EXISTS (select 1
      from patient_table t2
      where
            (t2.disease  like '%HIV%' OR 
            t2.disease  like '%COPD%') and
            t.patient_id = t2.patient_id)


patient_id
disease


hashB
diabetes

hashB
FSGS


select t.*
from patient_table t
   where exists (select 1
      from patient_table t2
      where t2.disease like '%diabetes%'  and
            t.patient_id = t2.patient_id
)
AND (
        select count(patient_id)
        from patient_table 
        where (disease  like '%HIV%' OR 
            disease  like '%COPD%') AND patient_id = t.patient_id
)<2


patient_id
disease


hashB
diabetes

hashB
FSGS