RDB/1 An introduction to RDBMS Objectives –To learn about the history and future direction of the SQL standard –To get an overall appreciation of a modern RDBMS and the nature of SQL –Familiarisation with the course environment and data to be used Contents –The need for a SQL standard –What is a Relational Database? –Components of a Relational Database –What does unnormalised/normalised data mean? –Anatomy of a table –Keys –Joins –What is ‘set oriented’? –The components of SQL92 (SQL2)

RDB/2 The need for a SQL standard Ted Codd’s Paper 1970’s - Various IBM Products Oracle -1st Commercial Implementation SQL/DS for DOS/VSE Environment DB2 for MVS Environment ANSI Standard for SQL ANSI SQL with Integrity Enhancement ISO/ANSI SQL2 SQL3

RDB/3 What is a Relational Database? Database Data Base Management System (The engine) Dynamic SQL Interactive SQL Interactive SQL Static SQL Names and Addresses Sales Data Design Information Libraries Drawings Satellite Images Production Schedules

RDB/4 Components of a Relational Database Database sysobjects sp_get_sales tr_sale_insert Stored Procedures dept sale User Tables ci_emp_deptno sales_by_dept Triggers System Tables Views Indexes

RDB/5 Anatomy of a table - (unnormalised) Need to uniquely identify each row via a mandatory ‘Primary Key’ column How do we: –Add new dept ‘3’ that has no employees yet ?? –Remove the ‘Sue Brown’ row but keep the ‘sales’ dept –Change the name of ‘Marketing’, without having to do it in many places emp_no fname lname dept_no dept_name 10 fred smith 1 marketing 20 bob james 1 marketing 30 sue brown 2 sales A table to hold all the data about departments and employees:

RDB/6 Anatomy of table(s) - (normalised) Multiple tables, one for each entity One occurrence of each entity is a row of a table Just sufficient duplication of data maintained to keep links between tables What about the three anomalies? –Add dept ‘3’ to the ‘dept’ table –Delete ‘Sue Brown’ from ‘employee’ table –Change the name of ‘marketing’ emp_no fname lname dept_no 10 fred smith 1 20 bob james 1 30 sue brown 2 dept_no dept_name 1 marketing 2 sales ‘employee’ table ‘department’ table

RDB/7 Keys - Primary & Foreign and ‘RI’ There exists a one to many relationship between ‘departments’ and ‘employees’ A Foreign Key of the ‘many’ table has values in it that must be in the Primary Key column of the ‘one’ table This concept is known as Referential Integrity (RI) We tell the RDBMS how to enforce this integrity in CREATE TABLE code (ch. 6) Declarative Referential Integrity is that feature of the RDBMS that implements RI in the CREATE TABLE statements emp_no fname lname dept_no 10 fred smith 1 20 bob james 1 30 sue brown 2 dept_no dept_name 1 marketing 2 sales ‘employee’ table (many) ‘department’ table (one) Primary Key Foreign Key Primary Key

RDB/8 Joins (sneak preview) Use ‘Key’ columns for Joins PK of the ‘one’ to FK of the ‘many’ –Some exceptions Choose a person and decide what dept he/she is in –You have just done a Join! (see chapter 5 for details) emp_no fname lname dept_no 10 fred smith 1 20 bob james 1 30 sue brown 2 dept_no dept_name 1 marketing 2 sales employee table (‘many’)department table (‘one’) Foreign Key Primary Key Parent Table Dependent Table

RDB/9 SQL is ‘set oriented’ SQL always operates on, and results in, complete sets of data - ‘rectangles’ of rows and columns SQL is ‘set oriented’ also when you add, change or delete data. For example: DELETE FROM employees Result: all employee records are removed emp_no fname lname dept_no 10 fred smith 1 20 bob james 1 30 sue brown 2 dept_no dept_name 1 marketing 2 sales employeedepartment

RDB/10 Components of SQL2 Data Definition Language - DDL –CREATE, ALTER and DROP statements –Used for Tables, Views, Columns, Indexes, Databases Data Manipulation Language - DML –SELECT, INSERT, UPDATE, DELETE statements –95% of SQL is probably DML statements –>95% of all DML statements are SELECT’s Data Control Language - DCL –Security for database usage –GRANT and REVOKE statements Programming Interface –PROCEDURES, TRIGGERS, CURSORS, TRANSACTIONS, LOCKING –Database specific, non standard, beyond the scope of this course

RDB/11 Practical Familiarisation with Query Analyzer - an MS SQL Server 2000 ‘interactive query’ client application –You will spend all your lab time on this course in Query Analyzer Familiarisation with the schema and data you will be working with on this course –‘depts’ employ ‘salespersons’ who make ‘sales’ to ‘contacts’ who work for ‘companies’ (our customers) –Each of you has a userid (sqluser’n’) with password of ‘password’ –Each of you has a ‘database’ (Database’n’) with 5 tables, each populated with data

RDB/12 Summary A Database –Enables storage and manipulation of data without an application A Relational Database –User data is stored and manipulated in sets called relations or tables –All system objects stored and manipulated the same way –Various types of system objects can be used for security/ performance enhancement –To take full advantage of the relational model and SQL, data is normalised –Tables have keys (Primary and Foreign) that can be used to join them at runtime The SQL Standard –Spread of RDBMS led to the need for a standard –Current standard SQL2 is widely implemented –All vendors offer proprietary extensions and alternatives