SQL Exercise: Find all physicians who completed a medical procedure

SQL hospital Database: Exercise-33 with Solution

33. From the following table, write a SQL query to find all physicians who completed a medical procedure with certification after the expiration date of their license. Return Physician Name as "Physician", Position as "Position".

 employeeid |       name        |           position           |    ssn
------------+-------------------+------------------------------+-----------
          1 | John Dorian       | Staff Internist              | 111111111
          2 | Elliot Reid       | Attending Physician          | 222222222
          3 | Christopher Turk  | Surgical Attending Physician | 333333333
          4 | Percival Cox      | Senior Attending Physician   | 444444444
          5 | Bob Kelso         | Head Chief of Medicine       | 555555555
          6 | Todd Quinlan      | Surgical Attending Physician | 666666666
          7 | John Wen          | Surgical Attending Physician | 777777777
          8 | Keith Dudemeister | MD Resident                  | 888888888
          9 | Molly Clock       | Attending Psychiatrist       | 999999999

 physician | treatment | certificationdate | certificationexpires
-----------+-----------+-------------------+----------------------
         3 |         1 | 2008-01-01        | 2008-12-31
         3 |         2 | 2008-01-01        | 2008-12-31
         3 |         5 | 2008-01-01        | 2008-12-31
         3 |         6 | 2008-01-01        | 2008-12-31
         3 |         7 | 2008-01-01        | 2008-12-31
         6 |         2 | 2008-01-01        | 2008-12-31
         6 |         5 | 2007-01-01        | 2007-12-31
         6 |         6 | 2008-01-01        | 2008-12-31
         7 |         1 | 2008-01-01        | 2008-12-31
         7 |         2 | 2008-01-01        | 2008-12-31
         7 |         3 | 2008-01-01        | 2008-12-31
         7 |         4 | 2008-01-01        | 2008-12-31
         7 |         5 | 2008-01-01        | 2008-12-31
         7 |         6 | 2008-01-01        | 2008-12-31
         7 |         7 | 2008-01-01        | 2008-12-31

 physician | treatment | certificationdate | certificationexpires
-----------+-----------+-------------------+----------------------
         3 |         1 | 2008-01-01        | 2008-12-31
         3 |         2 | 2008-01-01        | 2008-12-31
         3 |         5 | 2008-01-01        | 2008-12-31
         3 |         6 | 2008-01-01        | 2008-12-31
         3 |         7 | 2008-01-01        | 2008-12-31
         6 |         2 | 2008-01-01        | 2008-12-31
         6 |         5 | 2007-01-01        | 2007-12-31
         6 |         6 | 2008-01-01        | 2008-12-31
         7 |         1 | 2008-01-01        | 2008-12-31
         7 |         2 | 2008-01-01        | 2008-12-31
         7 |         3 | 2008-01-01        | 2008-12-31
         7 |         4 | 2008-01-01        | 2008-12-31
         7 |         5 | 2008-01-01        | 2008-12-31
         7 |         6 | 2008-01-01        | 2008-12-31
         7 |         7 | 2008-01-01        | 2008-12-31

Sample Solution:

SELECT name AS "Physician",
       position AS "Position"
FROM physician
WHERE employeeid IN
    ( SELECT physician
     FROM undergoes u
     WHERE date >
         ( SELECT certificationexpires
          FROM trained_in t
          WHERE t.physician = u.physician
            AND t.treatment = u.procedure ) );

Sample Output:

  Physician   |           Position
--------------+------------------------------
 Todd Quinlan | Surgical Attending Physician
(1 row)

Explanation:

This SQL query retrieves the names and positions of physicians whose certification has expired for a procedure they have performed.

The WHERE clause filters the results where the "employeeid" column is found in a subquery.

The WHERE clause of the subquery include only those records where the "date" column is greater than the certification expiration date for the procedure.

The certification expiration date is obtained from inner most subquery which selects the "certificationexpires" column from the 'trained_in' table where the physician and procedure match those in the outer subquery.

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E R Diagram of Hospital Database:

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Previous SQL Exercise: Doctors do the same procedure but are not certified.
Next SQL Exercise: Medical procedures done after certification expired.