SQL進階---第二單元(第一到第四課)、Manipulation
第二單元、Queries
第十一課、SELECT
QUERIES Queri
In this lesson you will be learningdifferent SQLcommands to query a single table in a database.
One of the core purposes of the SQL language is to retrieveinformation stored in a database. This is commonly referred to as querying.Queries allow us to communic-ate with the database by asking questions and having theresult set return data releva-nt to the question.
In this lesson, you will be querying a database with one tablenamed movies
.
Let's getstarted.
Instructions
1、Let's take a look at the nameand imdb_rating of every movie in thedatabase.
In the code editor type
SELECT name,imdb_ratin
FROM movies;
SELECT name,imdb_rating
FROM movies;
QueryResults
name |
imdb_rating |
Avatar |
7.9 |
Jurassic World |
7.3 |
The Avengers |
8.1 |
The Dark Knight |
9.0 |
Star Wars: Episode I - The Phantom Menace |
6.6 |
Star Wars |
8.7 |
Avengers: Age of Ultron |
7.9 |
The Dark Knight Rises |
8.5 |
Pirates of the Caribbean: Dead Mans Chest |
7.3 |
Iron Man 3 |
7.3 |
Spider-Man |
7.3 |
Transformers: Revenge of the Fallen |
6.0 |
Star Wars: Episode III - Revenge of the Sith |
7.7 |
Spider-Man 2 |
7.3 |
Transformers: Dark of the Moon |
6.3 |
American Sniper |
7.4 |
Furious Seven |
7.4 |
Spider-Man 3 |
6.2 |
Guardians of the Galaxy |
8.1 |
Transformers |
7.1 |
Iron Man |
7.9 |
Indiana Jones and the Kingdom of the Crystal Skull |
6.2 |
Iron Man 2 |
7.1 |
Star Wars: Episode II - Attack of the Clones |
6.7 |
Pirates of the Caribbean: At Worlds End |
7.1 |
Star Wars: Episode VI - Return of the Jedi |
8.4 |
Independence Day |
6.9 |
Pirates of the Caribbean: The Curse of the Black Pearl |
8.1 |
Skyfall |
7.8 |
Inception |
8.8 |
Man of Steel |
7.2 |
Star Wars: Episode V - The Empire Strikes Back |
8.8 |
The Matrix Reloaded |
7.2 |
The Amazing Spider-Man |
7.1 |
The Incredibles |
8.0 |
Captain America: The Winter Soldier |
7.8 |
The Lego Movie |
7.8 |
Star Trek |
8.0 |
Batman |
7.6 |
Night at the Museum |
6.4 |
Transformers: Age of Extinction |
5.8 |
Twister |
6.3 |
Maleficent |
7.0 |
Pirates of the Caribbean: On Stranger Tides |
6.7 |
Fast & Furious 6 |
7.2 |
Beverly Hills Cop |
7.3 |
X-Men: The Last Stand |
6.8 |
X-Men: Days of Future Past |
8.1 |
The Lost World: Jurassic Park |
6.5 |
Star Trek Into Darkness |
7.8 |
Shrek 2 |
7.2 |
Toy Story 3 |
8.4 |
Frozen |
7.6 |
Finding Nemo |
8.2 |
Despicable Me 2 |
7.5 |
Inside Out |
8.6 |
Shrek the Third |
6.0 |
Minions |
6.7 |
Up |
8.3 |
Monsters, Inc. |
8.1 |
Home Alone |
7.4 |
Meet the Fockers |
6.3 |
The Hangover |
7.8 |
Monsters University |
7.4 |
Shrek |
7.9 |
How the Grinch Stole Christmas |
6.0 |
The Hangover Part II |
6.5 |
Despicable Me |
7.7 |
Men in Black |
7.2 |
Toy Story 2 |
7.9 |
Cars |
7.2 |
Bruce Almighty |
6.7 |
My Big Fat Greek Wedding |
6.6 |
Shrek Forever After |
6.4 |
Brave |
7.2 |
Ghostbusters |
7.8 |
Rush Hour 2 |
6.6 |
Big Hero 6 |
7.9 |
Alvin and the Chipmunks: The Squeakquel |
4.4 |
Mrs. Doubtfire |
6.9 |
Ted |
7.0 |
Aladdin |
8.0 |
Alvin and the Chipmunks |
5.3 |
Madagascar 3: Europes Most Wanted |
7.0 |
Kung Fu Panda |
7.6 |
The Lorax |
6.5 |
Austin Powers in Goldmember |
6.2 |
Back to the Future |
8.5 |
Wedding Crashers |
7.0 |
Charlie and the Chocolate Factory |
6.7 |
Ratatouille |
8.0 |
Austin Powers: The Spy Who Shagged Me |
6.6 |
Tangled |
7.8 |
Monsters vs. Aliens |
6.6 |
Happy Feet |
6.5 |
Ice Age: Dawn of the Dinosaurs |
7.0 |
Ice Age: The Meltdown |
6.9 |
World War Z |
7.0 |
What Lies Beneath |
6.6 |
Gremlins |
7.2 |
The Blair Witch Project |
6.4 |
The Conjuring |
7.5 |
The Ring |
7.1 |
The Grudge |
5.9 |
Paranormal Activity |
6.3 |
Interview with the Vampire: The Vampire Chronicles |
7.6 |
Paranormal Activity 3 |
5.9 |
Scream |
7.2 |
Jaws 2 |
5.7 |
Scream 2 |
6.1 |
Sleepy Hollow |
7.4 |
The Others |
7.6 |
The Haunting |
4.9 |
Scream 3 |
5.5 |
Saw II |
6.6 |
The Amityville Horror |
6.2 |
Aliens |
8.4 |
Paranormal Activity 2 |
5.7 |
Annabelle |
5.4 |
Scooby-Doo 2: Monsters Unleashed |
4.9 |
Insidious: Chapter 2 |
6.6 |
Dracula |
7.5 |
Freddy vs. Jason |
5.8 |
Blade II |
6.7 |
Saw III |
6.2 |
The Texas Chainsaw Massacre |
6.2 |
Cloverfield |
7.1 |
Dark Shadows |
6.2 |
The Ring Two |
5.4 |
Zombieland |
7.7 |
Constantine |
6.9 |
The Exorcism of Emily Rose |
6.7 |
I Know What You Did Last Summer |
5.6 |
1408 |
6.8 |
Mama |
6.2 |
The Purge: Anarchy |
6.5 |
Scary Movie 2 |
5.2 |
Blade |
7.1 |
End of Days |
5.7 |
The Forgotten |
5.8 |
The Final Destination |
5.2 |
Warm Bodies |
6.9 |
Anaconda |
4.6 |
Wolf |
6.2 |
Friday the 13th |
5.6 |
The Purge |
5.6 |
Titanic |
7.7 |
Forrest Gump |
8.8 |
The Twilight Saga: Eclipse |
4.9 |
The Twilight Saga: New Moon |
4.6 |
The Twilight Saga: Breaking Dawn - Part 2 |
5.6 |
The Twilight Saga: Breaking Dawn - Part 1 |
4.9 |
Beauty and the Beast |
8.0 |
King Kong |
7.3 |
Ghost |
7.0 |
Cinderella |
7.1 |
Gone with the Wind |
8.2 |
Pearl Harbor |
6.0 |
Twilight |
5.2 |
Mr. & Mrs. Smith |
6.5 |
Snow White and the Seven Dwarfs |
7.7 |
What Women Want |
6.4 |
Top Gun |
6.8 |
Pretty Woman |
6.9 |
Hitch |
6.7 |
Tootsie |
7.4 |
Theres Something About Mary |
7.1 |
Elf |
6.9 |
Tarzan |
7.2 |
Bridesmaids |
6.8 |
Fifty Shades of Grey |
4.2 |
Robin Hood: Prince of Thieves |
6.9 |
The Proposal |
6.7 |
The Sound of Music |
8.0 |
Jerry Maguire |
7.3 |
Sex and the City |
5.5 |
Runaway Bride |
5.4 |
Les Misérables |
7.6 |
Knocked Up |
7.1 |
Little Fockers |
5.5 |
As Good as It Gets |
7.8 |
American Pie 2 |
6.4 |
The Great Gatsby |
7.3 |
Mamma Mia! |
6.4 |
Juno |
7.5 |
Marley & Me |
7.1 |
Pocahontas |
6.6 |
Slumdog Millionaire |
8.0 |
Look Whos Talking |
5.8 |
Click |
6.4 |
The Lion King |
8.5 |
Harry Potter and the Deathly Hallows: Part 2 |
8.1 |
The Sixth Sense |
8.2 |
Jaws |
8.1 |
I Am Legend |
7.2 |
The Blind Side |
7.7 |
Cast Away |
7.7 |
Signs |
6.7 |
Saving Private Ryan |
8.6 |
Dawn of the Planet of the Apes |
7.7 |
Interstellar |
8.7 |
Gladiator |
8.5 |
Dances with Wolves |
8.0 |
The Perfect Storm |
6.4 |
Lincoln |
7.4 |
Rise of the Planet of the Apes |
7.6 |
The Karate Kid |
6.2 |
Rain Man |
8.0 |
Air Force One |
6.4 |
True Grit |
7.7 |
A Beautiful Mind |
8.2 |
The Help |
8.1 |
3 Men and a Baby |
5.9 |
Gone Girl |
8.2 |
Kung Fu Panda 2 |
7.3 |
Hannibal |
6.7 |
Catch Me If You Can |
8.0 |
Big Daddy |
6.4 |
Se7en |
8.6 |
Seven |
6.1 |
DatabaseSchema
movies 220 rows |
|
id |
INTEGER |
name |
TEXT |
genre |
TEXT |
year |
INTEGER |
imdb_rating |
REAL |
第十二課、Select-l
QUERIES Select-II
SELECT name, imdb_rating
FROM movies;
In Lesson 1 you learned that SELECT
is
used every time you wantto query data from a database.
Multiplecolumns can be queried at once by separating column names with a comma. By specifying name,
imdb_rating
, the result set contains a name
and
imdb_rating
column.
Instructions
1.Let's continue with the SELECT
statement.
In the code editor, type
SELECT DISTINCT genre
FROM movies;
SELECT DISTINCT genre
FROM movies;
QueryResults
genre |
action |
comedy |
horror |
romance |
drama |
DatabaseSchema
movies 220 rows |
|
id |
INTEGER |
name |
TEXT |
genre |
TEXT |
year |
INTEGER |
imdb_rating |
REAL |
QUERIES Select Distinct
SELECT DISTINCT genre
FROM movies;
SELECT DISTINCT
is
used to return uniquevalues in the result set. It filters out all duplicate values. Here, the result set lists each genre in the movies
table
exactly once.
1. SELECT
DISTINCT
specifies that the statementis
going to be a query that returns unique values in the specified column(s)
2. genre
is
the name of the column to display in the result set.
3. FROM
movies
indicates the table name to query fro
Filtering the results of a query is an important skill in SQL.It is easier to see the different possible genres a movie can have after thedata has been filtered, than to scan every row in the table.
The rest of this lesson willteach you different commands in SQL to filter the results of a query.
1.The
way tofilter queries in SQL is to use the WHERE
clause.
In thecode editor type
SELECT * FROM movies WHERE imdb_rating > 8;
SELECT * FROM movies
WHEREimdb_rating > 8;
QueryResults
id |
name |
genre |
year |
imdb_rating |
3 |
The Avengers |
action |
2012 |
8.1 |
4 |
The Dark Knight |
action |
2008 |
9.0 |
6 |
Star Wars |
action |
1977 |
8.7 |
8 |
The Dark Knight Rises |
action |
2012 |
8.5 |
19 |
Guardians of the Galaxy |
action |
2014 |
8.1 |
26 |
Star Wars: Episode VI - Return of the Jedi |
action |
1983 |
8.4 |
28 |
Pirates of the Caribbean: The Curse of the Black Pearl |
action |
2003 |
8.1 |
30 |
Inception |
action |
2010 |
8.8 |
32 |
Star Wars: Episode V - The Empire Strikes Back |
action |
1980 |
8.8 |
48 |
X-Men: Days of Future Past |
action |
2014 |
8.1 |
52 |
Toy Story 3 |
comedy |
2010 |
8.4 |
54 |
Finding Nemo |
comedy |
2003 |
8.2 |
56 |
Inside Out |
comedy |
2015 |
8.6 |
59 |
Up |
comedy |
2009 |
8.3 |
60 |
Monsters, Inc. |
comedy |
2001 |
8.1 |
88 |
Back to the Future |
comedy |
1985 |
8.5 |
117 |
Aliens |
horror |
1986 |
8.4 |
148 |
Forrest Gump |
romance |
1994 |
8.8 |
157 |
Gone with the Wind |
romance |
1939 |
8.2 |
191 |
The Lion King |
drama |
1994 |
8.5 |
192 |
Harry Potter and the Deathly Hallows: Part 2 |
drama |
2011 |
8.1 |
193 |
The Sixth Sense |
drama |
1999 |
8.2 |
194 |
Jaws |
drama |
1975 |
8.1 |
199 |
Saving Private Ryan |
drama |
1998 |
8.6 |
201 |
Interstellar |
drama |
2014 |
8.7 |
202 |
Gladiator |
drama |
2000 |
8.5 |
211 |
A Beautiful Mind |
drama |
2001 |
8.2 |
212 |
The Help |
drama |
2011 |
8.1 |
214 |
Gone Girl |
drama |
2014 |
8.2 |
219 |
Se7en |
drama |
1995 |
8.6 |
DatabaseSchema
Movies 220 rows |
|
id |
INTEGER |
name |
TEXT |
genre |
TEXT |
year |
INTEGER |
imdb_rating |
REAL |
第十四課、Where
QUERIES Where
SELECT * FROM movies
WHERE imdb_rating > 8;
This statement filters the result set to only include movieswith IMDb ratings greater than 8. How does it work?
-
WHERE
is a clause that indicatesyou want to filter the result set to include only rows where the following condition is true.
2. imdb_rating>
8
is a condition that filters theresult set. Here, only rows with
a value greater than 8 in the imdb_rating
column
will be returned in the result set.
3. >
is
an operator. Operators create a condition that can be evaluated as eithertrue or false.
Commonoperators used with the WHERE
clause
are;
-
=
equals -
!=
not equals -
>
greater than -
<
less than -
>=
greater than or equal to -
<=
less than or equal to
There are also some specialoperators that we will learn more about in the upcoming exercises.
Instructions
1.LIKE
is
a special operator that can be used in a WHERE
clause.
In the code editor type
SELECT * FROM movies
WHERE name LIKE 'Se_en';
SELECT * FROM movies
WHEREname LIKE 'Se_en';
QueryResults
id |
name |
genre |
year |
imdb_rating |
219 |
Se7en |
drama |
1995 |
8.6 |
220 |
Seven |
drama |
1979 |
6.1 |
DatabaseSchema
Movies 220 rows |
|
id |
INTEGER |
name |
TEXT |
genre |
TEXT |
year |
INTEGER |
imdb_rating |
REAL |