SQL Exercise: Names of all patients who had at least 2 appointments

SQL hospital Database: Exercise-38 with Solution

38. From the following table, write a SQL query to find those patients with at least two appointments in which the nurse who prepared the appointment was a registered nurse and the physician who provided primary care should be identified. Return Patient name as "Patient", Physician name as "Primary Physician", and Nurse Name as "Nurse".

Sample table: appointment

Sample table: patient

Sample table: nurse

Sample table: physician

Sample Solution:

SELECT pt.name AS "Patient",
       p.name AS "Primary Physician",
       n.name AS "Nurse"
FROM appointment a
JOIN patient pt ON a.patient=pt.ssn
JOIN nurse n ON a.prepnurse=n.employeeid
JOIN physician p ON pt.pcp=p.employeeid
WHERE a.patient IN
    (SELECT patient
     FROM appointment a
     GROUP BY a.patient
     HAVING count(*)>=2)
  AND n.registered='true'
ORDER BY pt.name;

Sample Output:

    Patient    | Primary Physician |      Nurse
---------------+-------------------+-----------------
 Dennis Doe    | Christopher Turk  | Laverne Roberts
 Grace Ritchie | Elliot Reid       | Carla Espinosa
 Grace Ritchie | Elliot Reid       | Carla Espinosa
 John Smith    | John Dorian       | Carla Espinosa
 John Smith    | John Dorian       | Laverne Roberts
(5 rows)

Explanation:

The said query in SQL that selects the names of patients, their primary care physicians, and the names of the nurses who prepared for their appointments. The query only includes patients who have had at least two appointments and whose nurses are registered.

The query uses JOIN statements to link the tables based on the relevant columns. The JOIN statement combines the 'appointment' and 'patient' tables based on the patient and ssn columns. The second JOIN statement combines the 'appointment' and 'nurse' tables based on the presnurse and employeeid columns and the third JOIN statement links the 'patient' and 'physician' tables based on the pcp and employeeid columns.

With the first condition in WHERE clause, only patients with at least two appointments are included in the output, based on a subquery that groups and filters appointments by patient and the second condition ensures that only nurses who are registered are included in the output.

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E R Diagram of Hospital Database:

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