Chapter 4 - The Relational Algebra and Calculus presents about Relational Algebra (Unary Relational Operations, Relational Algebra Operations From Set Theory, Binary Relational Operations, Additional Relational Operations, Examples of Queries in Relational Algebra); Relational Calculus. | CSC271 Database Systems Lecture # 4 Summary: Previous Lecture ANSI-SPARC three-level architecture Schemas, mappings, and instances Data independence Database Languages Data sublanguage consist of two parts: DDL (Data Definition Language) DML (Data Manipulation Language) Data sublanguage Does not include constructs for all computing needs such as iterations or conditional statements Many DBMSs provide embedding the sublanguage in a high level programming language . C, C++, Java etc. In this case , these high level languages are called host languages Data Definition Language (DDL) Allows the DBA or user to describe and name entities, attributes, and relationships required for the application Plus any associated integrity and security constraints System catalog (data dictionary, data directory) Metadata (data about data, data description, data definitions) Data Manipulation Language (DML) Provides basic data manipulation operations on data held in the database Procedural DML Non-Procedural DML Procedural DML Allows user to tell system exactly how to manipulate data Operate on records individually Typically, embedded in a high level language Network or hierarchical DMLs More work is done by user (programmer) Non-Procedural DML Allows user to state what data is needed rather than how it is to be retrieved Operate on set of records Relational DBMS include . SQL, QBE etc. Easy to understand and learn than procedural DML More work is done by DBMS than user Provides considerable degree of data independence Also called declarative languages Fourth Generation Languages (4GLs) No clear consensus Forms generators Report generators Graphics generators Application generators Examples : SQL and QBE Functions of a DBMS Data storage, retrieval, and update A user-accessible catalog Transaction support Concurrency control services Recovery services Functions of a DBMS Authorization services Support for data communication Integrity service Services to promote data independence | CSC271 Database Systems Lecture # 4 Summary: Previous Lecture ANSI-SPARC three-level architecture Schemas, mappings, and instances Data independence Database Languages Data sublanguage consist of two parts: DDL (Data Definition Language) DML (Data Manipulation Language) Data sublanguage Does not include constructs for all computing needs such as iterations or conditional statements Many DBMSs provide embedding the sublanguage in a high level programming language . C, C++, Java etc. In this case , these high level languages are called host languages Data Definition Language (DDL) Allows the DBA or user to describe and name entities, attributes, and relationships required for the application Plus any associated integrity and security constraints System catalog (data dictionary, data directory) Metadata (data about data, data description, data definitions) Data Manipulation Language (DML) Provides basic data manipulation operations on data held in the database Procedural DML .
