SQL Demo: Selecting Data
We will work up to the primary table we want. Lets start with something a little bit less complex first. When working on these, keep in mind there are many ways to write equivalent SELECT statements, so your solution may be different from the one given.
Twitter Table
See if you can re-create the following table with a SELECT statement:
| name | |
|---|---|
| Greg Benson | @gregorydbenson |
| David Brizan | @davidguybrizan |
| Sophie Engle | @sjengle |
| Alark Joshi | @alark |
| Matthew Malensek | @MatthewMalensek |
| Terence Parr | @the_antlr_guy |
| Sami Rollins | @samirollins |
| David Wolber | @wolberd |
| Beste Yuksel | @BesteFYuksel |
See Answer.
SELECT
CONCAT(first, ' ', last) AS 'name',
CONCAT('@', twitterid) AS 'twitter'
FROM faculty_names
NATURAL JOIN faculty_twitter
ORDER BY faculty_names.last;Courses Table
Next, lets see if we can create a list of courses and who teaches them. It is easier to start by just counting the number of people that teach each course:
| course | professors |
|---|---|
| CS 107 | 4 |
| CS 110 | 4 |
| CS 112 | 5 |
| CS 212 | 3 |
| CS 220 | 2 |
| CS 221 | 1 |
| CS 245 | 3 |
| CS 315 | 2 |
| CS 326 | 2 |
| CS 336 | 1 |
| CS 345 | 2 |
| CS 360 | 2 |
| CS 411 | 1 |
| CS 490 | 3 |
See Answer.
SELECT
course,
COUNT(usfid) AS 'professors'
FROM faculty_courses
NATURAL LEFT OUTER JOIN faculty_names
GROUP BY course
ORDER BY course, last;Now, we can move to the full table:
| course | professors |
|---|---|
| CS 107 | Jeffrey Johnson, Kristin Jones, David Wolber, Beste Yuksel |
| CS 110 | Jeffrey Johnson, Alark Joshi, David Wolber, Beste Yuksel |
| CS 112 | Alark Joshi, EJ Jung, Olga Karpenko, Sami Rollins, David Wolber |
| CS 212 | Sophie Engle, Olga Karpenko, Sami Rollins |
| CS 220 | Matthew Malensek, Peter Pacheco |
| CS 221 | Vahab Pournaghshband |
| CS 245 | David Brizan, EJ Jung, Olga Karpenko |
| CS 315 | Greg Benson, Peter Pacheco |
| CS 326 | Greg Benson, Matthew Malensek |
| CS 336 | Vahab Pournaghshband |
| CS 345 | Kristin Jones, Terence Parr |
| CS 360 | Sophie Engle, Alark Joshi |
| CS 411 | Peter Pacheco |
| CS 490 | Jeffrey Johnson, Olga Karpenko, Beste Yuksel |
See Answer.
SELECT
course,
GROUP_CONCAT(
CONCAT(first, ' ', last)
ORDER BY last
SEPARATOR ', '
) AS 'professors'
FROM faculty_courses
NATURAL LEFT OUTER JOIN faculty_names
GROUP BY course
ORDER BY course, last;Faculty Table
Next, we can try and combine everything together. As before, I suggest you first work on a query that just gives counts:
| name | courses | ||
|---|---|---|---|
| Greg Benson | benson@usfca.edu | 2 | 2 |
| David Guy Brizan | dgbrizan@usfca.edu | 1 | 1 |
| Sophie Engle | sjengle@usfca.edu | 2 | 2 |
| Jeffrey Johnson | jajohnson9@usfca.edu | 0 | 3 |
| Kristin Jones | kjones12@usfca.edu | 0 | 2 |
| Alark Joshi | apjoshi@usfca.edu | 3 | 3 |
| EJ Jung | ejung2@usfca.edu | 0 | 2 |
| Olga Karpenko | okarpenko@usfca.edu | 0 | 4 |
| Matthew Malensek | mmalensek@usfca.edu | 2 | 2 |
| Peter Pacheco | peter@usfca.edu | 0 | 3 |
| Terence Parr | tjparr@usfca.edu | 1 | 1 |
| Vahab Pournaghshband | vpournaghs@usfca.edu | 0 | 2 |
| Sami Rollins | snrollins@usfca.edu | 2 | 2 |
| David Wolber | wolberd@usfca.edu | 3 | 3 |
| Beste Yuksel | byuksel@usfca.edu | 3 | 3 |
See Answer.
SELECT
CONCAT(first, ' ', IFNULL(CONCAT(middle, ' '), ''), last) AS 'name',
CONCAT(usfid, '@usfca.edu') AS 'email',
COUNT(twitterid) AS 'twitter',
COUNT(course) AS 'courses'
FROM faculty_names
NATURAL LEFT OUTER JOIN faculty_twitter
NATURAL LEFT OUTER JOIN faculty_courses
GROUP BY faculty_names.usfid
ORDER BY faculty_names.last;Now, we can work on creating the final version of our output:
| name | courses | ||
|---|---|---|---|
| Greg Benson | benson@usfca.edu | @gregorydbenson | CS 315, CS 326 |
| David Guy Brizan | dgbrizan@usfca.edu | @davidguybrizan | CS 245 |
| Sophie Engle | sjengle@usfca.edu | @sjengle | CS 212, CS 360 |
| Jeffrey Johnson | jajohnson9@usfca.edu | CS 107, CS 110, CS 490 | |
| Kristin Jones | kjones12@usfca.edu | CS 107, CS 345 | |
| Alark Joshi | apjoshi@usfca.edu | @alark | CS 110, CS 112, CS 360 |
| EJ Jung | ejung2@usfca.edu | CS 112, CS 245 | |
| Olga Karpenko | okarpenko@usfca.edu | CS 112, CS 212, CS 245, CS 490 | |
| Matthew Malensek | mmalensek@usfca.edu | @MatthewMalensek | CS 220, CS 326 |
| Peter Pacheco | peter@usfca.edu | CS 220, CS 315, CS 411 | |
| Terence Parr | tjparr@usfca.edu | @the_antlr_guy | CS 345 |
| Vahab Pournaghshband | vpournaghs@usfca.edu | CS 221, CS 336 | |
| Sami Rollins | snrollins@usfca.edu | @samirollins | CS 112, CS 212 |
| David Wolber | wolberd@usfca.edu | @wolberd | CS 107, CS 110, CS 112 |
| Beste Yuksel | byuksel@usfca.edu | @BesteFYuksel | CS 107, CS 110, CS 490 |
See Answer.
SELECT
CONCAT(first, ' ', IFNULL(CONCAT(middle, ' '), ''), last) AS 'name',
CONCAT(usfid, '@usfca.edu') AS 'email',
IFNULL(CONCAT('@', twitterid), '') AS 'twitter',
GROUP_CONCAT(course ORDER BY course SEPARATOR ', ') AS 'courses'
FROM faculty_names
NATURAL LEFT OUTER JOIN faculty_twitter
NATURAL LEFT OUTER JOIN faculty_courses
GROUP BY faculty_names.usfid
ORDER BY faculty_names.last;