sql queries basics. rhs – soc 2 sql query an sql query is an sql statement, which specifies a...
TRANSCRIPT
RHS – SOC 2
SQL query
• An SQL query is an SQL statement, which specifies a subset of the data in the database
• A subset in terms of– Tables– Fields– Conditions on fields
RHS – SOC 3
SQL query
• We use a movie information database as example
Movie movieid title country prodyear genre oscars
Actor actorid name country birth living oscars
Casting movieid actorid
RHS – SOC 4
SQL querymovieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
RHS – SOC 5
SQL query
• The most basic SQL query looks like:
SELECT <fieldlist>
FROM <tablename>
Which fields do I want
From what table do I want the fields
RHS – SOC 6
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT title, prodyearFROM Movie
RHS – SOC 7
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT title, prodyearFROM Movie
RHS – SOC 8
SQL query
title prodyear
E.T. 1982
Taxi 1998
Hunger 1966
Leon 1994
Hard Boiled 1992
1984 1984
Seven 1995
SELECT title, prodyearFROM Movie
RHS – SOC 9
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT movieid, title, country,…FROM Movie
RHS – SOC 10
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM Movie
* means ”all fields”
RHS – SOC 11
SQL query
• A slightly more complex SQL statement looks like:
SELECT <fieldlist>
FROM <tablename>
WHERE <condition>
Which fields do I want
From what table do I want the fields
What conditions must the fields fulfill
RHS – SOC 12
SQL query
• The WHERE part is a logical expression, specifying conditions on certain fields
• Five fundamental types of criteria– Comparison (<, > , =)– Range (< AND >)– Set membership (belongs to a set of values)– Pattern match (for string fields)– Null (is the value of the field a null value)
RHS – SOC 13
SQL query
• Note that we can build arbitrarily complex logical expressions, using the usual logical operators: AND, OR, NOT
• Rules are the same as for logical expres-sions in Java
• Use () to make expressions easier to read, and/or to ”overrule” evaluation rules
RHS – SOC 14
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE prodyear < 1990
RHS – SOC 15
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE prodyear < 1990
RHS – SOC 16
SQL query
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
3 Hunger Denmark 1966 Drama 1
6 1984 UK 1984 Sci-Fi 2
SELECT *FROM MovieWHERE prodyear < 1990
RHS – SOC 17
SQL query
title prodyear genre
E.T. 1982 Sci-Fi
Hunger 1966 Drama
1984 1984 Sci-Fi
SELECT title, prodyear, genreFROM MovieWHERE prodyear < 1990
RHS – SOC 18
Exercise 1 – SQL queries
• Create a MovieInformation database, as defined in the presentation
• Add records to the Movie table, as defined in the presentation
• With the data in place, run the below queries on the database– SELECT * FROM Movie WHERE (oscars = 1)– SELECT title, prodyear, oscars FROM Movie WHERE (country = ’USA’)– SELECT title, prodyear, genre FROM Movie WHERE (prodyear >= 1995)– SELECT * FROM Movie WHERE ((oscars = 0) AND (country = ’USA’))
• Now formulate queries yourself, in order to retrieve the below data:– Get all fields for movies where the genre is ’Action’– Get all fields for movies that did not win any Oscars– Get title, year and genre for movies from after 1993– Get title, year for movies that were not made in USA– Get all fields for all movies from before 1983 that won an Oscar– Get all fields for movies from either USA or UK that won an Oscar
RHS – SOC 19
SQL query - range
• A range search is an SQL query where a value should be within a certain range
• Actually just a two-part comparision query
SELECT *
FROM Movie
WHERE ((prodyear <= 1992) AND (prodyear >= 1980))
RHS – SOC 20
SQL query - range
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE ((prodyear<= 1992) AND (prodyear >= 1980))
RHS – SOC 21
SQL query - range
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE ((prodyear<= 1992) AND (prodyear >= 1980))
RHS – SOC 22
SQL query - range
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
SELECT *FROM MovieWHERE ((prodyear<= 1992) AND (prodyear >= 1980))
RHS – SOC 23
SQL query - range
• Another notation for range seach uses the keyword BETWEEN
SELECT *
FROM Movie
WHERE prodyear BETWEEN 1980 AND 1992
RHS – SOC 24
SQL query - range
• We can create a ”negated” version of a range query using NOT BETWEEN
SELECT *
FROM Movie
WHERE prodyear NOT BETWEEN 1980 AND 1992
RHS – SOC 25
SQL query – set membership
• A set membership search is an SQL query where a value must belong to a given set of values
• We use the IN keyword
SELECT *
FROM Movie
WHERE genre IN (’Action’,’Drama’)
RHS – SOC 26
SQL query – set membership
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE genre IN (’Action’,’Drama’)
RHS – SOC 27
SQL query – set membership
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE genre IN (’Action’,’Drama’)
RHS – SOC 28
SQL query – set membership
movieid title country prodyear genre oscars
3 Hunger Denmark 1966 Drama 1
5 Hard Boiled HK 1992 Action 0
SELECT *FROM MovieWHERE genre IN (’Action’,’Drama’)
RHS – SOC 29
SQL query – set membership
• Note that these two queries are equivalent
SELECT *
FROM Movie
WHERE genre IN (’Action’,’Drama’)
SELECT *
FROM Movie
WHERE ((genre = ’Action’) OR (genre = ’Drama’))
RHS – SOC 30
SQL query – set membership
• We can create a ”negated” version of a set membership query using NOT IN
SELECT *
FROM Movie
WHERE genre NOT IN (’Action’,’Drama’)
RHS – SOC 31
Exercise 2 – SQL queries
• Use the MovieInformation database, defined in exercise 1• With the data in place, run the below queries on the database
– SELECT * FROM Movie WHERE ((oscars > 0) AND (oscars < 3))
– SELECT * FROM Movie WHERE prodyear BETWEEN 1990 AND 1995
– SELECT * FROM Movie WHERE genre NOT IN (’Drama’, ’Sci-Fi’)
– SELECT * FROM Movie WHERE oscars IN (0,2,4)
• Now formulate queries yourself, in order to retrieve the below data:– Get movies made before 1980 or after 1990
– Get movies from USA made between 1985 and 1995
– Get movies winning at most 1 Oscar, in the genre Thriller’ or ’Sci-Fi’
– Get movies made in USA, HK or Denmark
– Get movies that won 2 or 4 Oscars, made before 1990
RHS – SOC 32
SQL query – pattern match
• A pattern match search is an SQL query where a (string) value must match a given pattern
• We use the LIKE keyword
• The hard part is choosing the correct pattern to match against – several ways to formulate a pattern
RHS – SOC 33
SQL query – pattern match
• A pattern is formulated using two special characters % and _
• % : wildcard: any sequence of zero or more characters
• _ : any single character
RHS – SOC 34
SQL query – pattern match
Pattern Meaning
’s%’ Any string starting with ’S’, of any length (at least 1)
(’super’, ’s’, ’s123’, ’s 123’)
’s_ _ _’ Any string starting with ’S’, of length exactly 4
(’such’, ’s123’, ’ssss’, ’s 1’)
’%s’ Any string ending with ’s’, of any length (at least 1)
(’Spurs’, ’s’, ’123s’, ’ s’, ’1 2s’)
’%s%’ Any string containing an ’s’, of any length (at least 1)
(’Spurs’, ’s’, ’basin’, ’ s ’, ’12s34’)
’%s_ _ _% Exercise…
RHS – SOC 35
SQL query – pattern match
SELECT *
FROM Movie
WHERE title LIKE ’H%’
SELECT *
FROM Movie
WHERE title LIKE ’_ _ _ _’
RHS – SOC 36
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE title LIKE ’H%’
RHS – SOC 37
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE title LIKE ’H%’
RHS – SOC 38
SQL query – pattern match
movieid title country prodyear genre oscars
3 Hunger Denmark 1966 Drama 1
5 Hard Boiled HK 1992 Action 0
SELECT *FROM MovieWHERE title LIKE ’H%’
RHS – SOC 39
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE title LIKE ’_ _ _ _’
RHS – SOC 40
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger Denmark 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled HK 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven USA 1995 Thriller 1
SELECT *FROM MovieWHERE title LIKE ’_ _ _ _’
RHS – SOC 41
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
4 Leon France 1994 Thriller 0
6 1984 UK 1984 Sci-Fi 2
SELECT *FROM MovieWHERE title LIKE ’_ _ _ _’
RHS – SOC 42
SQL query – pattern match
• We can create a ”negated” version of a pattern match query using NOT LIKE
SELECT *
FROM Movie
WHERE title NOT LIKE ’H%’
RHS – SOC 43
SQL query – null
• A null search is an SQL query where a value must be a null value
• We use the IS NULL keyword
• A null value…?
• We may allow a field to have an ”unde-fined” or null value, if it makes sense
RHS – SOC 44
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger <null> 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled <null> 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven <null> 1995 Thriller 1
SELECT *FROM MovieWHERE country IS NULL
RHS – SOC 45
SQL query – pattern match
movieid title country prodyear genre oscars
1 E.T. USA 1982 Sci-Fi 4
2 Taxi France 1998 Comedy 0
3 Hunger <null> 1966 Drama 1
4 Leon France 1994 Thriller 0
5 Hard Boiled <null> 1992 Action 0
6 1984 UK 1984 Sci-Fi 2
7 Seven <null> 1995 Thriller 1
SELECT *FROM MovieWHERE country IS NULL
RHS – SOC 46
SQL query – pattern match
movieid title country prodyear genre oscars
3 Hunger <null> 1966 Drama 1
5 Hard Boiled <null> 1992 Action 0
7 Seven <null> 1995 Thriller 1
SELECT *FROM MovieWHERE country IS NULL
RHS – SOC 47
SQL query – pattern match
• We can create a ”negated” version of a null query using IS NOT NULL
SELECT *
FROM Movie
WHERE country IS NOT NULL
RHS – SOC 48
Exercise 3 – SQL queries
• Use the MovieInformation database, defined in exercise 1• With the data in place, run the below queries on the database
– SELECT * FROM Movie WHERE title LIKE ’%a%’– SELECT * FROM Movie WHERE title LIKE ’%n’– SELECT * FROM Movie WHERE title LIKE ’%_ _ _ _ _ %’– SELECT * FROM Movie WHERE country IS NOT NULL
• Now formulate queries yourself, in order to retrieve the below data:– Get movies with a title containing an ’i’– Get movies with a title starting with ’A’, ’T’ or ’S’– Get movies with a title shorter than 6 characters– Get movies with a title containing an ’e’ and an ’r’– Get movies with a title consisting of more than one word