sql success ch03

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SQL Success

Chapter 3 slides

Stéphane Faroult

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select * from tablename

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select * from movies

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All columns

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variable1

variable2

variable3

Row Data

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select movie_id, title, year_released, country_code from movies

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select * from table

≈

print table

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Restriction

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Restriction

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Restriction

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Restriction

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where ...

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where country = 'us' select * from movies

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'constant'

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column

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Jaws where title =

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Jaws where title =

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'Jaws' where title =

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Movies

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Movies

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US Movies

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select * from movies where country = 'us'

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select * from movies where country = 'us'

select * from (select * from movies where country = 'us') us_movies where year_released between 1940 and 1949

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ALL MOVIES

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US MOVIES

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US MOVIES, 1940s

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select * from (select * from movies where year_released between 1940 and 1949) movies_from_the_1940s where country = 'us'

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select * from movies where country = 'us' and year_released between 1940 and 1949

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or

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or not

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select * from movies where country = 'us' or country = 'gb'

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and > or

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and > or

2 + 3 * 4

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and > or

2 + 3 * 4 3 * 4

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and > or

2 + 3 * 4

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3 * 4

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2 + 12

and > or

2 + 3 * 4

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3 * 4

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2 + 12

and > or

2 + 3 * 4

14

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where country = 'us' or country = 'gb' and year_released between 1940 and 1949

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where country = 'us' or country = 'gb' and year_released between 1940 and 1949

country = 'gb' and year_released between 1940 and 1949

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Movies

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Movies

1940s

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where (country = 'us' or country = 'gb') and year_released between 1940 and 1949

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French movies from the 1940s

plus

American movies from the 1950s

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select * from movies where (country = 'fr' and year_released between 1940 and 1949) or (country = 'us' and year_released between 1950 and 1959)

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=

<> or !=

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=

<= <

<> or !=

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=

<= <

>

<> or !=

>=

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2 < 10

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2 < 10

'2' < '10'

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2 < 10

'2' < '10'

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2 < 10

'2' < '10'

'2-JUN-1883'>'1-DEC-2056'

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2 < 10

'2' < '10'

'2-JUN-1883'>'1-DEC-2056'

As strings!

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DD/MM/YYYY

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DD/MM/YYYY

MM/DD/YYYY

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Convert EXPLICITLY!

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where issued = <some date>

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Flickr:Yoppy & Rudolf Schuba

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Flickr:Yoppy & Rudolf Schuba

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where issued >= and issued <=

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<Monday 00:00:00> <Friday 00:00:00>


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<Monday 00:00:00> <Friday 00:00:00>


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Sun Mon Tue Wed Thu Fri Sat

40

41

42

43

44

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27 28 29 30 1 2 3

4 5 6 7 8 9 10

11 12 13 14 15 16 17

18 19 20 21 22 23 24

25 26 27 28 29 30 31

1 2 3 4 5 6 7

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Sun Mon Tue Wed Thu Fri Sat

40

41

42

43

44

45

27 28 29 30 1 2 3

4 5 6 7 8 9 10

11 12 13 14 15 16 17

18 19 20 21 22 23 24

25 26 27 28 29 30 31

1 2 3 4 5 6 7

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year_released between 1940 and 1949

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year_released between 1940 and 1949

year_released >= 1940 and year_released <= 1949

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where country in ('us', 'gb') and year_released between 1940 and 1949


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country not in ('us', 'gb')

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like

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like

%

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like

% _

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select * from movies where title not like '%A%' and title not like '%a%'

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select * from movies where upper(title) not like '%A%'

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select * from movies where upper(title) not like '%A%'

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if (ptr == NULL) {

…

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if (ptr == NULL) {

…

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NULL in SQL is NOT a value …

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where column_name = null

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where column_name = null

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where column_name <> null

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where column_name <> null

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where column_name is null

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where column_name is null

where column_name is not null

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Who are the people in the database who are alive?

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select title, year_released from movies where country = 'us'

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databases - +

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databases -

schemas +

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databases -

schemas +

tables +

-

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databases -

schemas +

tables +

columns +

-

-

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desc movies;

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desc movies;

describe table movies

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desc movies;


\d movies

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desc movies;


\d movies

.schema movies

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compute

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compute

derive

107 Flickr: Etsuko Nakamura

108 Flickr: Etsuko Nakamura

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'hello' ' world' +

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'hello' ' world' ||

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concat( , ) 'hello' ' world'

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select title || ' was released in ' || year_released movie_release from movies where country = 'us'

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select title || ' was released in ' || year_released movie_release from movies where country = 'us'

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select title + ' was released in ' + cast(year_released as varchar) movie_release from movies where country = 'us'

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select concat(title, ' was released in ', year_released) movie_release from movies where country = 'us'

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people

Age of people alive?

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people born died

Age of people alive?

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Alive

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died

Alive is null

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died

Alive is null

Age

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died

Alive is null

Age born <this year> -

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select from some_table where some_column = some_user_input

column1, ...

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f(column1), ...

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f(column1), ...

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select from some_table where some_column = f(some_user_input)

column1, ...

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select from some_table where f(some_column) = some_user_input

column1, ...

127 Flickr:Tony Austin

case end

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Y

n

color case upper(color) when 'Y' then 'Color' when 'N' then 'B&W' else '?' end as color, ...

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Y

n


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Y

n


Color

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case upper(color) when 'Y' then 'Color' when 'N' then 'B&W' else '?' end as color, ...

Y

n

color

Color

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Y

n

color

Color

?

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Y

n

color

Color

B&W

?

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Y

n

color

Color

B&W

?

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case column_name when null then end

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case column_name when null then end

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case upper(color) when 'Y' then 'Color' when 'N' then 'B&W' else '?' end as color,

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when 1929 then 'passed away'

case died when 1920 then 'passed away' when 1921 then 'passed away'








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case when died is null then 'alive and kicking' else 'passed away' end as status

died is null

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Flickr:Sanath Kumar

Some useful functions

more in appendix B ...

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round( )

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round(

trunc(

)

)

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round(

trunc( )

3 3.141592, 0)

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round(

trunc( 3.141592)

3

3

3.141592, 0)

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3.141592, 3) round(

trunc( 3.141592)

3.142

3

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3.141592, 3)

3.141592, 3) round(

trunc(

3.142

3.141

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upper(), lower()

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substr(

upper(), lower()

)

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substr(

upper(), lower()

'Citizen Kane', 5, 3)

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substr(

trim(

upper(), lower()

)

)

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substr(

trim(

upper(), lower()

)

' Oops ') 'Oops'

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substr(

trim(

replace(

upper(), lower()

)

)

)

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'Sheep', 'ee', 'i')

substr(

trim(

replace(

upper(), lower()

)

)

'Ship'

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upper(), lower()

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substring(

upper(), lower()

)

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substring(

upper(), lower()

'Citizen Kane', 5, 3)

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substring(

ltrim(

upper(), lower()

)

)

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substring(

ltrim(

upper(), lower()

)

' Oops ') 'Oops '

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substring(

ltrim(

upper(), lower()

)

' Oops ') 'Oops '

rtrim()

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substring(

ltrim(

replace(

upper(), lower()

)

)

)

rtrim()

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'Sheep', 'ee', 'i')

substring(

ltrim(

replace(

upper(), lower()

)

)

rtrim()

'Ship'

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Current date

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MARCH FEBRUARY

Current date

Date Arithmetic

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MARCH

Current date

Date Arithmetic

+ 1 month

+ 30 days

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dateadd(month, 1, date_col)

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date_col + 1 month

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date_col + 1 month

date_col + interval'1 month'

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date_col + 1 month


date_add(date_col, interval 1 month)

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date_col + 1 month



add_months(date_col, 1)

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date_col + 1 month




date_col + decimal_number

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date_col + 1 month




date_col + decimal_number

date(date_col, '1 month')

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'28-DEC-1895'

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'28-DEC-1895'

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'28-DEC-1895'

DBMS date

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'12/28/1895'

DBMS date

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cast( as )

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y z x

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(x + y)

z

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(x + y)

z

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No duplicates

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No duplicates

Identifier

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select country from movies

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distinct

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distinct

select distinct country from movies

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Aggregate functions

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select country, year_released, title from movies

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us 1942 Casablanca

us 1990 Goodfellas

ru 1925 Bronenosets Potyomkin

us 1982 Blade Runner

us 1977 Annie Hall

hk 1986 Ying hung boon sik

in 1975 Sholay

us 1954 On The Waterfront

gb 1962 Lawrence Of Arabia

gb 1949 The Third Man

it 1948 Ladri di biciclette

us 1941 Citizen Kane

de 1985 Das Boot

se 1957 Det sjunde inseglet

fr 1997 Le cinquième élément

it 1966 Il buono, il brutto, il cattivo

jp 1954 Shichinin no Samurai

in 1955 Pather Panchali

nz 2001 The Lord of the Rings

fr 1946 La belle et la bête

...


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de 1985 Das Boot



fr 1942 Les Visiteurs du Soir




in 1975 Sholay








us 1942 Casablanca

us 1990 Goodfellas


us 1977 Annie Hall


...


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de 1985 Das Boot







in 1975 Sholay








us 1942 Casablanca

us 1990 Goodfellas


us 1977 Annie Hall


...


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group by

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group by

select country, count(*) number_of_movies from movies group by country

count(*)

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group by


country

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group by


country

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de 1985 Das Boot







in 1975 Sholay








us 1942 Casablanca

us 1990 Goodfellas


us 1977 Annie Hall


...


1

3

2

1

2

2

1 1

1 1

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select country, year_released, count(*) number_of_movies from movies group by country, year_released

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select country, year_released, count(*) number_of_movies from movies group by country, year_released

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select count(*) number_of_movies from movies

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where

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where

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where

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where

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where

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distinct, group by

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distinct, group by

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distinct, group by

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distinct, group by

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distinct, group by

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count(*)

min(

max(

avg(

count(col)

col)

col)

col)

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Earliest release year by country?

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select country, min(year_released) oldest_movie from movies group by country

Earliest release year by country?

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select * from ( ) earliest_movies_per_country where oldest_movie < 1940

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having

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having min(year_released) < 1940

having

219 Flickr: Randy Robertson

SORT

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group by country having country = 'us'

select country, min(year_released) oldest_movie from movies

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where country = 'us' group by country

select country, min(year_released) oldest_movie from movies

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having

Result of aggregate

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Nulls?

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Nulls?

known + unknown = unknown

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FLickr: Linda Åslund

Aggregate functions

ignore Nulls

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select max(died) most_recent_death from people

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select max(died) most_recent_death from people where died is not null

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count(*)

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count(*)

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count(col)

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count(col)

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select count(*) people_count, count(born) birth_year_count, count(died) death_year_count from people

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select count(colname)

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select count(distinct colname)

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select country, count(distinct year_released) number_of_years from movies group by country

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select country, count(*) number_of_years from (select distinct country, year_released from movies) t group by country

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How many people are both

actors and directors?

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credits

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8 37 D 8 38 A 8 39 A 8 40 A 10 11 A 10 12 A 10 15 D 10 16 A 10 17 A 12 11 A 12 11 D 12 12 A 136 378 D 136 433 A 136 434 A 136 435 A 115 38 A 115 359 D 115 360 A ...

movieid peopleid credited_as

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select peopleid, credited_as from credits

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38 A

38 A


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38 A

38 A

11 A

11 A


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peopleid credited_as

11 A 11 D 12 A 15 D 16 A 17 A 37 D 38 A 39 A 40 A 359 D 360 A 361 A 378 D 379 A 380 A 442 A 442 D 443 A ...

select distinct peopleid, credited_as from credits where credited_as in ('A', 'D')

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( ) all_actors_and_directors


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select peopleid, count(*) as number_of_roles from group by peopleid having count(*) = 2



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select peopleid, count(*) as number_of_roles from group by peopleid having count(*) = 2



select count(*) number_of_acting_directors from (

) acting_directors

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Rows are selected with where + conditions. Beware of or. Beware of nulls. Beware of dates.

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Rows are selected with where + conditions. Beware of or. Beware of nulls. Beware of dates. Many functions. case ... end for conditional display.

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Rows are selected with where + conditions. Beware of or. Beware of nulls. Beware of dates. Many functions. case ... end for conditional display.

You must use distinct or group by to remove duplicates from a result set if there is no key.

sql success ch03

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