Minimize SQL queries - php

Question

I have created a php code for listing the patients who have
1-email
2-zero future treatments
3-equal to or more than 1 finished treatments
4-latest finished treatment date is equal to 3 weeks ago from today
The problem is, I have more than 50K patients and for each patient, querying the above conditions taking a lot of time.
Is there a way of merging the sql queries into one, rather than for every patient having 3 or more queries which makes around 200k queries?
the code is below:
$today = date('Y-m-d');
$three_weeks_ago = date('Y-m-d', strtotime($today.'-3 weeks'));
$patients = $db->query("
SELECT
dg_patients_patients.id,
dg_patients_patients.first_name,
dg_patients_patients.last_name,
dg_patients_patients.email,
dg_clinics.clinic_name,
dg_clinics.clinic_address,
dg_clinics.clinic_phone
FROM dg_patients_patients
LEFT JOIN dg_clinics ON dg_patients_patients.clinic_id = dg_clinics.id
WHERE dg_patients_patients.email <> '' ORDER BY dg_patients_patients.first_name ASC ");
$now = date('Y-m-d H:i:s');
foreach ($patients as $row){
$patientID = $row['id'];
//Get Patient Future Treatments
$check_future_treatments = $db->column("SELECT id FROM dg_patient_treatment_finance WHERE treatment_type = :a1 AND patient_id = :a2 ",array("a1"=>"1","a2"=>"$patientID"));
$future_treatments = count($check_future_treatments);
//Get Patient Finished Treatments
$check_finished_treatments = $db->column("SELECT id FROM dg_patient_treatment_finance WHERE treatment_type = :a1 AND patient_id = :a2 ",array("a1"=>"2","a2"=>"$patientID"));
$finished_treatments = count($check_finished_treatments);
if($future_treatments == 0 && $finished_treatments > 0 ) {
$latest_finished_treatment_date = $db->single("SELECT plan_date FROM dg_patient_treatment_finance WHERE patient_id = :pid ORDER BY plan_date DESC LIMIT 1 ", array("pid"=>"$patientID"));
if($latest_finished_treatment_date == $three_weeks_ago){
echo $patientID.'- '.$row['first_name'].' '.$row['last_name'].' - '.$row['email'].'<br>';
}
}

Answer 1

You could try to LEFT JOIN on dg_patient_treatment_finance, use a GROUP BY and use SUM in combination with the CASE statement.
And at the same time calculate the MAX plan_date.
SELECT
p.id, p.first_name, p.last_name, p.email,
c.clinic_name, c.clinic_address, c.clinic_phone,
SUM(case when tf.treatment_type = 1 then 1 else 0 end) as total_treatment_type_1,
SUM(case when tf.treatment_type = 2 then 1 else 0 end) as total_treatment_type_2,
MAX(tf.plan_date) as max_plan_date
FROM dg_patients_patients p
LEFT JOIN dg_clinics c ON (p.clinic_id = c.id)
LEFT JOIN dg_patient_treatment_finance tf ON (p.id = tf.patient_id and tf.treatment_type IN (1,2))
WHERE p.email <> ''
GROUP BY
p.id, p.first_name, p.last_name, p.email,
c.clinic_name, c.clinic_address, c.clinic_phone
ORDER BY p.first_name, p.last_name
Then you can also simplify the calculation of $future_treatments and $finished_treatments by taking the content from the calculated sums.