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• Data Definition Language - Used by the DBA and database designers to specify the description of the database.
• Data Definition Language

  CREATE TABLE student(

  name VARCHAR2(50),

  student_no NUMBER(9),

  classification VARCHAR2(9)

  );
• Data Manipulation Language - Used to specify database retrievals and

  updates (insertion, deletion and modification of data)
• Data Manipulation Language

  SELECT * from student;

  INSERT INTO student values ('Mariang Banga', 202212345, 'JUNIOR');

  UPDATE student set classification = 'SENIOR' where name = 'Mariang Banga';
• Data Control Language - Used to control and provide levels of access

  privileges and authorization to database objects.
• DBMS Interfaces

  • Stand-alone query language interfaces
  • Programmer interfaces for embedding DML in programming languages
  • User-friendly interfaces
  • Menu-based, popular for browsing on the web
• DBMS Interfaces

  • Forms-based, designed for naïve users
  • Graphics-based
  • Natural language: requests in written English
  • Speech as Input and Output
  • Parametric interfaces, e.g., bank tellers using function keys.
• DDL Compiler -Process DDL statements and stores database description in the DBMS catalog
• Privileged Commands - Commands used only by the DBA or the DBA staff. These includes commands for creating accounts, granting account authorization, changing database description, etc.
• Query Compiler - Parses queries, analyzes queries for correctness of operations and names of data elements, and compiles them into an internal form
• Query Optimizer - Concerned with the rearrangement and possible reordering of operations, elimination of redundancies and use of correct algorithms during execution.
• Query Optimizer - Generates executable code and makes calls on the runtime processor
• Precompiler - Extracts DML commands from an application program
• DML Compiler - Parses DML statements and translates them into an object code
• Host Language Compiler - Parses and compiles host language statements
• Compiled Transaction - Canned transactions that is based on the object codes produced by the DML and host language compiler
• Runtime Database Processor - Executes privileged commands, executable query plans and canned transactions with runtime parameters
• Stored Data Manager - Controls access to the information stored on the disk
• Stored Data Manager - Interacts with the Operating System to carry put low-level input/output operations between the disk and main memory
• DBMS Architecture

  • Centralized
  • Client-Server
• Centralized DBMS - Combines everything into single system including- DBMS software, hardware, application programs, and user interface processing software.
• Centralized DBMS - User can still connect through a remote terminal – however, all processing is done at centralized site.
• Client-server DBMS - Composed of two parts: the client and the server
• Client - A user machine that provides user interface capabilities and local processing.
• Client - May be diskless machines or PCs or Workstations with disks with only the client software installed.
• Client - Connected to the servers via some form of a network.
• Types of Client

  • Thin
  • Thick
• Thin client - Dependent on another machine (e.g., server) to complete a process
• Thick client - Can provide functionality independent of the server
• Examples of specialized Servers with Specialized functions

  ❏ Print server

  ❏ File server

  ❏ Web server

  ❏ Email server

  ❏ DBMS server
• Clients can access the specialized servers as needed
• Server - A system containing both hardware and software that can provide services to the client machines such as file access, printing, archiving or database access
• Two Tier Client-Server Architecture

  1st Approach - Client contains the user interface and application programs. Server contains the DBMS
• Two Tier Client-Server Architecture

  2nd Approach - The DBMS was divided into client and server. Client may handle user interface, application programs, data dictionary functions, DBMS interactions with the compilers, query optimizer, etc.
• Two Tier Client-Server Architecture

  2nd Approach - Server may include software responsible for handling data storage on disks, buffering of disk pages, etc. (also known as data server)
• Three-Tier Client-Server Architecture

  ❏ The client communicates with the application server usually through a form's interface.

  ❏ The application server stores the business rules (procedures) that are used to access data from the database.

  ❏ The database server will provide the data.
• Three-tier Architecture Can Enhance Security:

  ❏ Database server is only accessible via middle tier

  ❏ Clients cannot directly access database server
• Database Schema - The description of a database. Includes descriptions of the database structure, data types, and the constraints on the database.
• Schema Diagram - An illustrative display of (most aspects of) a database schema.
• Schema Construct - A component of the schema or an object within the schema, e.g., STUDENT, COURSE.