Download SQL as a Data Definition Language

Outline
SQL : Structured Query Language
data definition language
Introduction
Data Definition
Integrity constraints
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slide 152
slide 159
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SQL presentation
Introduction
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SQL Presentation (2)
Functionalities :
data definition and data manipulation in the relational format
data control
Manipulation language
non procedural
borrowed to relational algebra and to the tuple relational calculus
Power of the manipulation language
Relational Algebra
+
Functions-Aggregates + Sorting
A SQL query (without functions and sorting)
Set of Relational Algebra operations
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SQL as DDL
Introduction
History
SEQUEL language of the SYSTEM/R relational DBMS
prototype (74-76)
IBM research lab at San José
Normalization at ISO
The SQL1 norm (1986, 1989)
The SQL2 norm (1992)
The SQL3 norm
Query language of (quite) all relational DBMSs
ORACLE (Oracle Corporation - 1977)
INGRES (Ingres Technology - 1980)
DB2 (IBM - 1984)
INFORMIX (Informix Inc - 1981)
SYBASE (Sybase Inc - 1984)
MySQL (1995)
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Data Definition
Data Definition
Relation Schema Definition
Relational View Definition
Integrity Constraint Definition
Right Definition
Validation Process
data storage and index definition
(not normalized => DBMS dependent !!)
SQL DDL vs. Relational Model
A finite set of domains
optional key:
Duplicate rows
The projection operator is different (
DISTINCT)
A Relation is not a set
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Basic Domains
Numeric :
Data Definition
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Relation Schema
INTEGER, SMALLINT
DECIMAL (m,n), NUMBER(m,n)
FLOAT, REAL
Data Definition
Creation
CREATE TABLE Project (
ProjNumber Integer ,
ProjName Char(20),
PLocation Char(40) )
String : CHAR (n), VARCHAR(n)
Temporal : DATE (SQL2 ! norm )
Specific DBMS have their own domains
NULL : missing value
Evolution
add an attribute (SQL2 ! norm)
ALTER TABLE Project ADD COLUMN DepNumber Integer
Delete (SQL2 ! norm )
DROP TABLE Project
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SQL as DDL
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Movie database example
Movie database example (2)
Movies(id, title, yr, score, votes, director)
Directors(id, name)
Actors(id, name)
Castings(movieid, actorid, ord)
Movies
score
id
title
yr
score
0,n
Castings
ord
0,n
Actors
idactor
nameactor
1,1
IsDirectedBy
0,n
Directors
iddirector
namedirector
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Example
CREATE TABLE MOVIES (
id integer,
title char (40),
yr integer ,
score integer,
votes integer,
director integer))
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Integrity constraints
CREATE TABLE CASTINGS (
movieid integer,
actorid integer,
ord integer)
Business rules for data
Consistent state of the database
Enforced at any time
CREATE TABLE ACTORS (
id integer,
name char(40)
)
CREATE TABLE DIRECTORS (
id integer,
name char(40))
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SQL as DDL
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Integrity constraints examples
Integrity constraints and DBMS
Relational data model:
Domain:
MOVIES(id, title, yr, score, votes, director)
ACTORS(id, name)
ord between 1 and 10
yr between 1900 and 2005
Behavioral:
the value of votes is always increasing
SQL
SQL extensions
What about commercial DBMS ?
DIRECTORS(id, name)
At schema definition (mainly)
During schema lifecycle
How to express IC ?
Not null
actor’s name is mandatory
CASTINGS(movieid, actorid, ord)
key uniqueness (id in MOVIES)
foreign key (director to DIRECTORS)
Movie database schema
When ?
Just a few ICs
Other ICs supported by programs (triggers)
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Example
Integrity constraints and DBMS (2)
CREATE TABLE MOVIES (
id integer PRIMARY KEY,
title char (40) NOT NULL,
yr integer CONSTRAINT ICyr
CHECK (yr between 1900 and 2005),
score integer CONSTRAINT ICscore
CHECK (score between 0 and 10),
votes integer NOT NULL ,
director integer))
Norms:
SQL86 : unicity, not null, view with «check option »
SQL89 : domain, key, referential integrity with reject
SQL2 (SQL92) : referential integrity with «cascade delete
and update »
Integrity constraints definition
2 different syntaxes:
At the end of an attribute definition
At the end of a table definition
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SQL as DDL
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CREATE TABLE CASTINGS (
movieid integer,
actorid integer,
ord integer CONSTRAINT ICord
CHECK (ord between 1 and 10))
ALTER TABLE CASTINGS
add primary key (movieid, actorid)
ALTER TABLE CASTINGS
add constraint fkACT
foreign key (actorid) references
ACTORS(id) on delete cascade
CREATE TABLE ACTORS (
id integer,
name char(40)
PRIMARY KEY(id) )
ALTER TABLE CASTINGS
add constraint fkMOV
foreign key (movieid) references
MOVIES(id) on delete cascade
CREATE TABLE DIRECTORS (
id integer PRIMARY KEY,
name char(40))
ALTER TABLE MOVIES
add constraint fkDIR
foreign key (director) references
DIRECTORS(id) on delete cascade
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Problems with integrity constraints
Consistency of a set of IC
No contradictory rules
Redundancy
Age > 18 and age > 21
Optimisation
Determine the minimum set of data concerned by a IC
enforcement
Determine the minimum set of IC to verify after a database
update
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SQL as DDL
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