SQL Exercise: Doctors do the same procedure but are not certified

SQL hospital Database: Exercise-32 with Solution

32. From the following tables, write a SQL query to find all physicians, their procedures, the date when the procedure was performed, and the name of the patient on whom the procedure was performed, but the physicians are not certified to perform that procedure. Return Physician Name as "Physician", Procedure Name as "Procedure", date, and Patient. Name as "Patient".

Sample table: physician

Sample table: undergoes

Sample table: patient

Sample table: procedure

Sample table: trained_in

Sample Solution:

SELECT p.name AS "Physician",
       pr.name AS "Procedure",
       pt.name AS "Patient"
FROM physician p,
     undergoes u,
     patient pt,
WHERE u.patient = pt.SSN
  AND u.procedure = pr.Code
  AND u.physician = p.EmployeeID
    ( SELECT *
     FROM trained_in t
     WHERE t.treatment = u.procedure
       AND t.physician = u.physician );

Sample Output:

    Physician     |       Procedure       |        date         |  Patient
 Christopher Turk | Complete Walletectomy | 2008-05-13 00:00:00 | Dennis Doe
(1 row)	


The said query in SQL that retrieves the name of the physician, the procedure name and the date, and the name of the patient about procedures performed by physicians who have not been trained in that procedure.

The WHERE clause uses to join the tables 'undergoes' and 'patient' based on the patient and SSN columns, and the tables 'undergoes' and 'procedure' based on the procedure and code columns, and the tables 'undergoes' and 'physician' based on the physician and employee ID columns.

The NOT EXISTS keyword filters out the result of a subquery. The subquery searches the 'trained_in' table for a record with the same procedure code and physician ID as the current record in the 'undergoes' table. If a record is found, the subquery returns true and the current record is excluded from the result set.

Practice Online

E R Diagram of Hospital Database:

E R Diagram: SQL Hospital Database.

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Previous SQL Exercise: Physicians, a medical procedure without certification.
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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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