SQL Exercise: Patients with their doctors and medications

SQL hospital Database: Exercise-20 with Solution

20. From the following tables, write a SQL query to identify patients who have made an advanced appointment. Return Patient name as "Patient", Physician name as "Physician" and Medication name as "Medication".

Sample table: patient

Sample table: prescribes

Sample table: physician

Sample table: medication

Sample Solution:

SELECT t.name AS "Patient",
       p.name AS "Physician",
       m.name AS "Medication"
FROM patient t
JOIN prescribes s ON s.patient=t.ssn
JOIN physician p ON s.physician=p.employeeid
JOIN medication m ON s.medication=m.code
WHERE s.appointment IS NOT NULL;

Sample Output:

  Patient   |  Physician  |  Medication
 John Smith | John Dorian | Procrastin-X
 Dennis Doe | Molly Clock | Thesisin
(2 rows)


The said query in SQL that returns information about medications prescribed to patients during their appointments, including the patient's name, the physician's name, and the medication name.

The query performs a join between the 'patient', 'prescribes', 'physician', and 'medication' tables, based on their relational columns.

The 'prescribes' and 'patient' tables are joins based on the patient and ssn columns, the 'prescribes' and 'physician tables are joins based on the physician and employeeid columns, and the 'medication ' and the 'prescribes' and 'medication' tables are joins based on the medication and code columns.

The included WHERE clause filters the results by medications that were prescribed during appointments. This is determined by checking whether the appointment identifier in the 'prescribes' table is not NULL.

Practice Online

E R Diagram of Hospital Database:

E R Diagram: SQL Hospital Database.

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Previous SQL Exercise: Names of patients, their doctors, and medications.
Next SQL Exercise: Find patients without an appointment.

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SQL: Tips of the Day

Grouped LIMIT in PostgreSQL: Show the first N rows for each group?

db=# SELECT * FROM xxx;
 id | section_id | name
  1 |          1 | A
  2 |          1 | B
  3 |          1 | C
  4 |          1 | D
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
  8 |          2 | H
(8 rows)

I need the first 2 rows (ordered by name) for each section_id, i.e. a result similar to:

id | section_id | name
  1 |          1 | A
  2 |          1 | B
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
(5 rows)

PostgreSQL v9.3 you can do a lateral join

select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer
join lateral (
    select * from t t_inner
    where t_inner.section_id = t_outer.section_id
    order by t_inner.name
    limit 2
) t_top on true
order by t_outer.section_id;

Database: PostgreSQL

Ref: https://bit.ly/3AfYwZI


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