ISO6 Relational Databases Simon Booth Room Library S6 Tel: 7247

PF Lecture 1 2 Course Aims Develop a basic proficiency in A relational database environment The SQL database language – Oracle SQL*Plus A forms-based 4GL programming tool – Access 97 Database design and Management

PF Lecture 1 3 Lectures and Workshops Lectures (A1)  Monday Workshop (2A19)  Monday 14-16

PF Lecture 1 4 Applications and Books SQL Plus Oracle 3.3/8.0 Oracle 8 database Access 97 Database Design and Management by Nick Dowling (Letts) £10.99

PF Lecture 1 5 Proposed Course Structure First half – SQL Plus version 3.3/8.0 running against Oracle 8 Second half – Access 97 Lecture on Monday – practical issues on the upcoming workshops

PF Lecture 1 6 Database Management Systems (DBMS) Definition “ A set of programs that act as an interface between application programs and the data in the database”

PF Lecture 1 7 users/programmers Software to process Queries/Programs Software to access Stored Data A Simplified Database System Environment Application Programs/Queries Database System DBMS Software Stored Database Definition (Meta-Data) Stored Database

PF Lecture primary functions of a DBMS Define, create and organize a database (Data Definition Language) Input data Process data (Data Manipulation Language) Maintain Data integrity and security Query database (Structured Query Language)

PF Lecture 1 9 Advantages of DBMS Data independence  Access to data based on its contents and its associations with other data Physical organization of data is independent of program using it Reduction in data redundancy Accessing and processing data more effective DATA users

PF Lecture 1 10 Disadvantages of DBMS Cost is the primary disadvantage Mainframe hardware expensive Even expensive with PC based databases  Licences  Training  Maintenance and Management

PF Lecture 1 11 Database Infrastructures Hierarchical Network Relational

PF Lecture 1 12 Hierarchical ROOT Father Son 2Son 1

PF Lecture 1 13 Network Owner Member

PF Lecture 1 14 Relational Model

PF Lecture 1 15 Structured Query Language (SQL) Programming language (4GL) Data definition and data manipulation language Used in all types of database applications Oracle and Access

PF Lecture 1 16 SQL (cont.) Provided a degree of homogeneity Industry standard Databases conforming to the SQL standard can also use applications from other SQL databases SQL standards approved by ANSI Incorporating SQL technology provides a strong selling point

PF Lecture 1 17 SQL Plus (Sequel Plus) SQL*Plus is a program for working with an ORACLE database  Create tables  Store information in the tables  Retrieve information in a form you choose, performing calculations on it and combining it in new ways  Maintain the database

Querying & Manipulating Databases Using SQL*Plus

PF Lecture 1 19 Accessing SQL*Plus 3.3 To access Oracle SQL*Plus you must first log-on in the normal way. In Windows NT go to START, PROGRAMS, ORACLE, ORACLE WinNT, SQL Plus 3.3.

PF Lecture 1 20 Accessing SQL Enter your oracle username and password. You will also be asked for a ‘host string’ enter ora1a11

PF Lecture 1 21 Accessing SQL Having entered these, you will then see the SQL prompt from Oracle: SQL> You are now ready to type SQL commands

PF Lecture 1 22 Accessing SQL SQL>SELECT job FROM emp 2 Note: Oracle itself is not case- sensitive. I have used a mixture of upper and lower case to indicate SQL commands (uppercase) and the components I select (lowercase)

PF Lecture 1 23 Accessing SQL SQL>SELECT job FROM emp 2 Note: Oracle inserts the “2” to indicate that we are on the second line. To properly terminate the command, enter ;. Oracle will now process the command.

PF Lecture 1 24 A table ArtistTitleFormat VerveUrban HymnsCD OasisBe Here NowCassette RadioheadBendsCD The above is a table named called “music” with three columns: Artist, Title and Format. There are presently three rows.

PF Lecture 1 25 The Select command To list the columns Artist and Format from the table music: SQL> SELECT artist, format FROM music;

PF Lecture 1 26 The WHERE clause We can select based on rows that meet a certain condition. For instance, only CD’s: SQL> SELECT * FROM music 2 WHERE format LIKE ‘CD’; * means all columns

PF Lecture 1 27 The WHERE clause(2) Another Example: SQL> SELECT ename, deptno, sal 2 FROM emp 3 WHERE sal >= 1500; Columns are listed in the order they appear and can appear more than once

PF Lecture 1 28 The ORDER BY clause Oracle will list back the information we ask in order it appears in the table. If we want it alphabetically or by numerical order we must add an ORDER BY and specify the column(s) to order by.

PF Lecture 1 29 The ORDER BY clause(2) Example: SQL> SELECT ename, deptno, sal 2 FROM emp 3 ORDER BY sal DESC;

PF Lecture 1 30 SQL Group Functions These functions (AVG, MAX, MIN, etc) can act on entire tables or subsets of the table SELECT AVG(sal) FROM emp; SELECT MAX(sal) FROM emp WHERE job = ‘MANAGER’; SELECT COUNT(*) FROM emp WHERE deptno = 20;

PF Lecture 1 31 GROUP BY Group functions can also be used with the GROUP BY clause, which splits the table into specified groups, returning one row for each group SELECT AVG(sal), deptno FROM emp GROUP BY deptno;

PF Lecture 1 32 Clauses Clauses can be combined: SQL> SELECT ename, deptno, sal 2 FROM emp 3 WHERE sal > ORDER BY sal DESC;

PF Lecture 1 33 Second example Rows maybe selected by WHERE SELECT AVG(sal), deptno FROM emp WHERE job != ‘MANAGER’ GROUP BY deptno;

PF Lecture 1 34 Update The SQL command update is used to modify all or some rows in the table: UPDATE table SET column = expr [, column = expr] [WHERE condition];

PF Lecture 1 35 Update Example: correct name for employee 7369 UPDATE emp SET ename = ‘jones’ WHERE empno = 7369;

PF Lecture 1 36 Delete The SQL command delete is used to remove all or some rows in the table: DELETE FROM table [WHERE condition];

PF Lecture 1 37 Delete Example: remove employee 7369 DELETE FROM emp WHERE empno = 7369;

PF Lecture 1 38 Copying Tables We can copy tables existing tables: CREATE TABLE stolen_table AS SELECT * FROM another_table;

PF Lecture 1 39 Creating Tables(2) If we only want specific columns, we name them in the select; If we only want specific rows, we use a WHERE clause: CREATE TABLE stolen_table AS SELECT video_no, title FROM video WHERE title = ‘T%’;

PF Lecture 1 40 Populating Tables To place data in a table we use the INSERT command: INSERT INTO table [(column-name, …)] VALUES (value, … ); Which adds one row to the table. To add more, we have more INSERT commands

PF Lecture 1 41 Populating Tables Examples: INSERT INTO dept (deptno, dname) VALUES (50, ‘Marketing’); INSERT INTO dept VALUES (50, ‘Marketing’, ‘Stirling’);

PF Lecture 1 42 Summary of SQL commands SQL  SELECT  UPDATE  DELETE  CREATE AS  INSERT