SQL DATABASE Module (Due in 8 hours)
budsimpson
chapt04.pdf
The One-to-Many
Relationship
Cow of many-well milked and
badly fed
Spanish proverb
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The one-to-many relationship
Entities are related to other entities
A 1:m relationship
3
Hierarchical relationships
Occur frequently
Multiple 1:m relationships
4
STOCK with additional columns
stock
stkcode stkfirm stkprice stkqty stkdiv stkpe natname exchrate
FC Freedonia Copper 27.50 10529 1.84 16 United Kingdom 1.00
PT Patagonian Tea 55.25 12635 2.50 10 United Kingdom 1.00
AR Abyssinian Ruby 31.82 22010 1.32 13 United Kingdom 1.00
SLG Sri Lankan Gold 50.37 32868 2.68 16 United Kingdom 1.00
ILZ Indian Lead &Zinc 37.75 6390 3.00 12 United Kingdom 1.00
BE Burmese Elephant .07 154713 0.01 3 United Kingdom 1.00
BS Bolivian Sheep 12.75 231678 1.78 11 United Kingdom 1.00
NG Nigerian Geese 35.00 12323 1.68 10 United Kingdom 1.00
CS Canadian Sugar 52.78 4716 2.50 15 United Kingdom 1.00
ROF Royal Ostrich Farms 33.75 1234923 3.00 6 United Kingdom 1.00
MG Minnesota Gold 53.87 816122 1.00 25 USA 0.67
GP Georgia Peach 2.35 387333 .20 5 USA 0.67
NE Narembeen Emu 12.34 45619 1.00 8 Australia 0.46
QD Queensland Diamond 6.73 89251 .50 7 Australia 0.46
IR Indooroopilly Ruby 15.92 56147 .50 20 Australia 0.46
BD Bombay Duck 25.55 167382 1.00 12 India 0.0228
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Create another entity to
avoid update anomalies
Insert
Delete
Update
6
Mapping to a relational
database
Each entity becomes a table
The entity name becomes the table name
Each attribute becomes a column
Add a column to the table at the many end of a 1:m relationship
Put the identifier of the one end in the added column
NATION and STOCK nation
natcode natname exchrate
UK United Kingdom 1.00
USA United States 0.67
AUS Australia 0.46
IND India 0.0228
stock
stkcode stkfirm stkprice stkqty stkdiv stkpe natcode
FC Freedonia Copper 27.50 10529 1.84 16 UK
PT Patagonian Tea 55.25 12635 2.50 10 UK
AR Abyssinian Ruby 31.82 22010 1.32 13 UK
SLG Sri Lankan Gold 50.37 32868 2.68 16 UK
ILZ Indian Lead &Zinc 37.75 6390 3.00 12 UK
BE Burmese Elephant .07 154713 0.01 3 UK
BS Bolivian Sheep 12.75 231678 1.78 11 UK
NG Nigerian Geese 35.00 12323 1.68 10 UK
CS Canadian Sugar 52.78 4716 2.50 15 UK
ROF Royal Ostrich Farms 33.75 1234923 3.00 6 UK
MG Minnesota Gold 53.87 816122 1.00 25 USA
GP Georgia Peach 2.35 387333 .20 5 USA
NE Narembeen Emu 12.34 45619 1.00 8 AUS
QD Queensland Diamond 6.73 89251 .50 7 AUS
IR Indooroopilly Ruby 15.92 56147 .50 20 AUS
BD Bombay Duck 25.55 167382 1.00 12 IND
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Foreign keys
A foreign key is a column that is a primary key of another table
natcode in stock is a foreign key because natcode is the primary key of nation
Records a 1:m relationship
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Referential integrity
constraint
For every value of a foreign key there is a primary key with that value
For every value of natcode in stock there is a value of natcode in nation
A primary key must exist before the foreign key can be defined
Must create the nation before its stocks
10
Creating the tables
CREATE TABLE nation (
natcode CHAR(3),
natname VARCHAR(20),
exchrate DECIMAL(9,5),
PRIMARY KEY (natcode));
CREATE TABLE stock (
stkcode CHAR(3),
stkfirm VARCHAR(20),
stkprice DECIMAL(6,2),
stkqty DECIMAL(8),
stkdiv DECIMAL(5,2),
stkpe DECIMAL(5),
natcode CHAR(3),
PRIMARY KEY(stkcode),
CONSTRAINT fk_has_nation FOREIGN KEY(natcode)
REFERENCES nation(natcode));
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Representing a 1:m relationship
in MySQL Workbench
A non-identifying relationship in
MySQL Workbench
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Representing a 1:m
relationship in MS Access
Exercise
Develop a data model to keep track of a distance runner’s times over various lengths
Create the database and add 3 rows for each of 2 athletes
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Join
Create a new table from two existing tables by matching on a common column
SELECT * FROM stock JOIN nation ON stock.natcode = nation.natcode;
stkcode stkfirm stkprice stkqty stkdiv stkpe natcode natcode natname exchrate NE Narembeen Emu 12.34 45619 1.00 8 AUS AUS Australia 0.46000
IR Indooroopilly Ruby 15.92 56147 0.50 20 AUS AUS Australia 0.46000
QD Queensland Diamond 6.73 89251 0.50 7 AUS AUS Australia 0.46000
BD Bombay Duck 25.55 167382 1.00 12 IND IND India 0.02280
ROF Royal Ostrich Farms 33.75 1234923 3.00 6 UK UK United Kingdom 1.00000
CS Canadian Sugar 52.78 4716 2.50 15 UK UK United Kingdom 1.00000
FC Freedonia Copper 27.50 10529 1.84 16 UK UK United Kingdom 1.00000
BS Bolivian Sheep 12.75 231678 1.78 11 UK UK United Kingdom 1.00000
BE Burmese Elephant 0.07 154713 0.01 3 UK UK United Kingdom 1.00000
ILZ Indian Lead & Zinc 37.75 6390 3.00 12 UK UK United Kingdom 1.00000
SLG Sri Lankan Gold 50.37 32868 2.68 16 UK UK United Kingdom 1.00000
AR Abyssinian Ruby 31.82 22010 1.32 13 UK UK United Kingdom 1.00000
PT Patagonian Tea 55.25 12635 2.50 10 UK UK United Kingdom 1.00000
NG Nigerian Geese 35.00 12323 1.68 10 UK UK United Kingdom 1.00000
MG Minnesota Gold 53.87 816122 1.00 25 US US United States 0.67000
GP Georgia Peach 2.35 387333 0.20 5 US US United States 0.67000
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Join
Report the value of each stock holding in UK pounds. Sort the report by nation and firm.
SELECT natname, stkfirm, stkprice, stkqty, exchrate,
stkprice*stkqty*exchrate AS stkvalue
FROM stock JOIN nation
ON stock.natcode = nation.natcode
ORDER BY natname, stkfirm;
natname stkfirm stkprice stkqty exchrate stkvalue Australia Indooroopilly Ruby 15.92 56147 0.46000 411175.71
Australia Narembeen Emu 12.34 45619 0.46000 258951.69
Australia Queensland Diamond 6.73 89251 0.46000 276303.25
India Bombay Duck 25.55 167382 0.02280 97506.71
United Kingdom Abyssinian Ruby 31.82 22010 1.00000 700358.20
United Kingdom Bolivian Sheep 12.75 231678 1.00000 2953894.50
United Kingdom Burmese Elephant 0.07 154713 1.00000 10829.91
United Kingdom Canadian Sugar 52.78 4716 1.00000 248910.48
United Kingdom Freedonia Copper 27.50 10529 1.00000 289547.50
United Kingdom Indian Lead & Zinc 37.75 6390 1.00000 241222.50
United Kingdom Nigerian Geese 35.00 12323 1.00000 431305.00
United Kingdom Patagonian Tea 55.25 12635 1.00000 698083.75
United Kingdom Royal Ostrich Farms 33.75 1234923 1.00000 41678651.25
United Kingdom Sri Lankan Gold 50.37 32868 1.00000 1655561.16
United States Georgia Peach 2.35 387333 0.67000 609855.81
United States Minnesota Gold 53.87 816122 0.67000 29456209.73
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GROUP BY - reporting by
groups
Report by nation the total value of stockholdings.
SELECT natname, SUM(stkprice*stkqty*exchrate) AS stkvalue
FROM stock JOIN nation ON stock.natcode = nation.natcode
GROUP BY natname;
natname stkvalue
Australia 946430.65
India 97506.71
United Kingdom 48908364.25
United States 30066065.54
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HAVING - the WHERE clause
of groups
Report the total value of stocks for nations with two or more listed stocks.
SELECT natname, SUM(stkprice*stkqty*exchrate) AS stkvalue
FROM stock JOIN nation ON stock.natcode = nation.natcode
GROUP BY natname
HAVING COUNT(*) >= 2;
natname stkvalue
Australia 946430.65
United Kingdom 48908364.25
United States 30066065.54
Exercise
Report the total dividend payment for each country that has three or more stocks in the portfolio
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Structure of SQL statements
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Regular expression
Search for a string not containing specified characters
[^a-f] means any character not in the set containing a, b, c, d, e, or f
This means the string 'abcdefg' will be reported because it contains a 'g', which is not in a-f
List the names of nations with non- alphabetic characters in their names
SELECT * FROM nation
WHERE natname REGEXP '[^a-z|A-Z]'
Regular expression
Search for a column not containing a specified character in any position in the column
^[^x]*$ means any character (*) from the first (^) through the last ($) is not x [^x]
List the names of nations without s or S anywhere in their names
SELECT * FROM nation WHERE natname
REGEXP '^[^s|S]*$'
Regular expression
Search for a string containing a repetition
{n} means repeat the pattern n times
List the names of firms with a double ‘e’.
SELECT * FROM stock
WHERE stkfirm REGEXP '[e]{2}'
Regular expression
Search for a string containing several different specified strings
| means alternation (or)
List the names of firms with a double ‘s’ or a double ‘n’.
SELECT * FROM stock
WHERE stkfirm REGEXP '[s]{2}|[n]{2}'
Regular expression
Search for multiple versions of a string
[ea] means any character from the set containing e and a
It will match for ‘e’ or ‘a’
List the names of firms with names that include ‘inia’ or ‘onia’.
SELECT * FROM stock
WHERE stkfirm REGEXP '[io]nia'
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Regular expression
Find firms with ‘t’ as the third letter of their name.
SELECT shrfirm FROM share
WHERE shrfirm REGEXP '^(.){2}t';
Find firms not containing an ‘s’ in their name.
SELECT shrfirm FROM share
WHERE shrfirm NOT REGEXP 's|S';
regexlib.com
A library of regular expressions
Cheat sheet for creating expressions
Regex Tester
Exercise
Report the names of nations starting with ‘United’
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Subqueries
A query nested within another query Report the names of all Australian stocks.
SELECT stkfirm FROM stock
WHERE natcode IN
(SELECT natcode FROM nation
WHERE natname = 'Australia');
stkfirm
Narembeen Emu
Queensland Diamond
Indooroopilly Ruby
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Correlated subquery
Solves the inner query many times
Find those stocks where the quantity is greater than the average for that country.
SELECT natname, stkfirm, stkqty FROM stock JOIN nation
ON stock.natcode = nation.natcode
AND stkqty >
(SELECT AVG(stkqty) FROM stock
WHERE stock.natcode = nation.natcode);
natname stkfirm stkqty Australia Queensland Diamond 89251
United Kingdom Bolivian Sheep 231678
United Kingdom Royal Ostrich Farms 1234923
United States
Minnesota Gold 816122
Correlated subqueries can be resource intensive
Correlated subquery SELECT natname, stkfirm, stkqty FROM stock JOIN nation
ON stock.natcode = nation.natcode
WHERE stkqty >
(SELECT AVG(stkqty) FROM stock
WHERE stock.natcode = nation.natcode);
Stock
stkcode stkfirm stkprice stkqty stkdiv stkpe natcode
NE Narembeen Emu 12.34 45619 1.00 8 AUS
IR Indooroopilly Ruby 15.92 56147 0.50 20 AUS
QD Queensland Diamond 6.73 89251 0.50 7 AUS
BD Bombay Duck 25.55 167382 1.00 12 IND
ROF Royal Ostrich Farms 33.75 1234923 3.00 6 UK
CS Canadian Sugar 52.78 4716 2.50 15 UK
FC Freedonia Copper 27.50 10529 1.84 16 UK
BS Bolivian Sheep 12.75 231678 1.78 11 UK
BE Burmese Elephant 0.07 154713 0.01 3 UK
ILZ Indian Lead & Zinc 37.75 6390 3.00 12 UK
SLG Sri Lankan Gold 50.37 32868 2.68 16 UK
AR Abyssinian Ruby 31.82 22010 1.32 13 UK
PT Patagonian Tea 55.25 12635 2.50 10 UK
NG Nigerian Geese 35.00 12323 1.68 10 UK
MG Minnesota Gold 53.87 816122 1.00 25 US
GP Georgia Peach 2.35 387333 0.20 5 US
JOIN
natname stkfirm stkqty
Australia Indooroopilly Ruby 56147
Australia Narembeen Emu 45619
Australia Queensland Diamond 89251
India Bombay Duck 167382
United Kingdom Abyssinian Ruby 22010
United Kingdom Burmese Elephant 154713
United Kingdom Bolivian Sheep 231678
United Kingdom Canadian Sugar 4716
United Kingdom Freedonia Copper 10529
United Kingdom Indian Lead & Zinc 6390
United Kingdom Nigerian Geese 12323
United Kingdom Patagonian Tea 12635
United Kingdom Royal Ostrich Farms 1234923
United Kingdom Sri Lankan Gold 32868
United States Georgia Peach 387333
United States Minnesota Gold 816122
Exercise
Report the country, firm, and stock holding for the maximum quantity of stock held for each country
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Views - virtual tables
An imaginary table constructed by the DBMS when required
Only the definition of the view is stored, not the result
CREATE VIEW stkvalue
(nation, firm, price, qty, exchrate, value)
AS SELECT natname, stkfirm, stkprice, stkqty, exchrate,
stkprice*stkqty*exchrate
FROM stock JOIN nation
ON stock.natcode = nation.natcode;
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Views - querying
Query exactly as if a table SELECT nation, firm, value
FROM stkvalue WHERE value > 100000;
nation firm value
United Kingdom Freedonia Copper 289547.50
United Kingdom Patagonian Tea 698083.75
United Kingdom Abyssinian Ruby 700358.20
United Kingdom Sri Lankan Gold 1655561.16
United Kingdom Indian Lead & Zinc 241222.50
United Kingdom Bolivian Sheep 2953894.50
United Kingdom Nigerian Geese 431305.00
United Kingdom Canadian Sugar 248910.48
United Kingdom Royal Ostrich Farms 41678651.25
United States Minnesota Gold 29456209.73
United States Georgia Peach 609855.80
Australia Narembeen Emu 258951.69
Australia Queensland Diamond 276303.24
Australia Indooroopilly Ruby 411175.71
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Why create a view?
Simplify query writing
Calculated columns
Restrict access to parts of a table
Exercise
Create a view for dividend payment
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Summary
New topics
1:m relationship
Foreign key
Correlated subquery
GROUP BY
HAVING clause
View
