SQL : Structured Query Language data definition language

Transcription

1 Outline SQL : Structured Query Language data definition language Introduction slide 150 slide 152 Integrity constraints slide SQL presentation Introduction SQL Presentation (2) Introduction 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 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 ) INGRES (Ingres Technology ) DB2 (IBM ) INFORMIX (Informix Inc ) SYBASE (Sybase Inc ) MySQL (1995) SQL as DDL 1

2 SQL DDL vs. Relational Model Relation Schema Definition Relational View Definition Integrity Constraint Definition Right Definition Validation Process data storage and index definition (not normalized => DBMS dependent!!) A finite set of domains optional key: Duplicate rows The projection operator is different ( DISTINCT) A Relation is not a set Basic Domains Relation Schema Numeric : INTEGER, SMALLINT DECIMAL (m,n), NUMBER(m,n) FLOAT, REAL String : CHAR (n), VARCHAR(n) Temporal : DATE (SQL2! norm ) Specific DBMS have their own domains NULL : missing value Creation CREATE TABLE Project ( ProjNumber Integer, ProjName Char(20), PLocation Char(40) ) Evolution add an attribute (SQL2! norm) ALTER TABLE Project ADD COLUMN DepNumber Integer Delete (SQL2! norm ) DROP TABLE Project SQL as DDL 2

3 Movie database example Movie database example (2) Movies(id, title, yr, score, votes, director) Directors(id, name) Actors(id, name) Castings(movieid, actorid, ord) score id title yr score Movies 1,1 Castings ord Actors idactor nameactor IsDirectedBy Directors iddirector namedirector Example CREATE TABLE MOVIES ( title char (40), yr integer, score integer, votes integer, director integer)) CREATE TABLE ACTORS ( name char(40) ) CREATE TABLE DIRECTORS ( name char(40)) CREATE TABLE CASTINGS ( movie actor ord integer) Integrity constraints Business rules for data Consistent state of the database Enforced at any time SQL as DDL 3

4 Integrity constraints examples Integrity constraints and DBMS Movie database schema MOVIES(id, title, yr, score, votes, director) ACTORS(id, name) CASTINGS(movieid, actorid, ord) DIRECTORS(id, name) Relational data model: key uniqueness (id in MOVIES) foreign key (director to DIRECTORS) Domain: ord between 1 and 10 yr between 1900 and 2005 Not null actor s name is mandatory Behavioral: the value of votes is always increasing When? At schema definition (mainly) During schema lifecycle How to express IC? SQL SQL extensions What about commercial DBMS? Just a few ICs Other ICs supported by programs (triggers) Integrity constraints and DBMS (2) 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 Example 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)) CREATE TABLE ACTORS ( name char(40) PRIMARY KEY(id) ) CREATE TABLE DIRECTORS ( id integer PRIMARY KEY, name char(40)) CREATE TABLE CASTINGS ( movie actor ord integer CONSTRAINT ICord CHECK (ord between 1 and 10)) add primary key (movieid, actorid) add constraint fkact foreign key (actorid) references ACTORS(id) on delete cascade add constraint fkmov foreign key (movieid) references MOVIES(id) on delete cascade ALTER TABLE MOVIES add constraint fkdir foreign key (director) references DIRECTORS(id) on delete cascade SQL as DDL 4

5 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 164 SQL as DDL 5