SQL essenziale

Applicare SQL a problemi reali

Dmitriy (Dima) Gorenshteyn

Lead Data Scientist, Memorial Sloan Kettering Cancer Center

Cosa imparerai!

Capitolo 1: Usa SQL nel mondo reale
Capitolo 2: Trova i tuoi dati
Capitolo 3: Gestisci i tuoi dati
Capitolo 4: Buone pratiche per scrivere SQL

Il database

Noleggio DVD
Basato sul database pagila $^1$

Tabelle
actor	film_actor
address	inventory
category	language
customer	payment
film	rental

Copyright (c) Devrim Gündüz <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated 
documentation files (the "Software"), to deal in the Software without restriction, including without limitation the 
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to 
permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of 
the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO 
THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.

¹ https://github.com/devrimgunduz/pagila

Comandi SQL essenziali

SELECT title, length
FROM film AS f
INNER JOIN category AS c
  ON f.film_id = c.film_id
WHERE c.category = 'Documentary'
  AND f.rating IN ('G', 'PG')
ORDER BY length DESC;

SELECT, FROM

SELECT title, length
FROM film




;

SELECT

SELECT <column1>, <column2>  
-- OR
SELECT *

FROM

FROM <table_name>

INNER JOIN

SELECT title, length
FROM film AS f
INNER JOIN category AS c
  ON f.film_id = c.film_id


;

<column_name> AS <alias1>

INNER JOIN

INNER JOIN <table_name> AS <alias2>

ON <alias1>.<column> = <alias2>.<column>

WHERE, AND, IN

SELECT title, length
FROM film AS f
INNER JOIN category AS c
  ON f.film_id = c.film_id
WHERE c.category = 'Documentary'
  AND f.rating IN ('G', 'PG')
;

WHERE

WHERE <condition>

AND

AND <condition>

IN ('<item1>', '<item2>', ...)

ORDER BY, DESC

SELECT title, length
FROM film AS f
INNER JOIN category AS c
  ON f.film_id = c.film_id
WHERE c.category = 'Documentary'
  AND f.rating IN ('G', 'PG')
ORDER BY length DESC;

ORDER BY

ORDER BY <column_name>

DESC

ORDER BY <column_name> DESC

Esercita l'essenziale!

Applicare SQL a problemi reali