SIT772 Database and Information Retrieval

Transcription

1 SIT772 Database and Information Retrieval Practical 2: Data Models (I) Relational Model Objectives: To learn how to use Microsoft Office Visio to draw ER diagrams To learn more SQL*Plus and SQL commands for table and data manipulation in a database 1. Using Microsoft Office Visio to Draw ER Diagrams In this session, we turn our attention from SQL commands in Oracle to Microsoft Office Visio to draw Entity-Relationship (ER) diagrams. Microsoft Office Visio is a professional software package for drawing various diagrams, including ER diagrams in database design. Open the Microsoft Office Visio tutorial on CloudDeakin If your computer has MS Visio 2010 installed, open the tutorial document Prac04_Visio2010.pdf. If your computer has MS Visio 2013 installed, open the tutorial document Prac04_Visio2013.pdf. then follow instructions in the tutorial to learn how to draw ER diagrams. After you finish this tutorial, you should be able to use this software to draw ER diagrams in database design. The next task is for you to draw an ER diagram. 1. Exercise of Drawing an ER Diagram Draw the following ER diagram (on the next page) using Microsoft Office Visio or any graphic applications. 1

2 SQL Introduction: In Practical 1, we learned - how to connect to an Oracle databases, - how to create tables in a database and populate tables with data by using SQL commands CREATE TABLE and INSERT INTO, - how to use SQL*Plus command DESCRIBE (or DESC) to view a table structure, - how to use SQL command SELECT to view the created tables in a database and the data in a table, and - how to quit the database. Generally speaking, at the prompt we can execute standard SQL commands we are going to introduce in this unit. In addition, Oracle also provides some SQL*Plus commands to manipulate objects in a database. Getting to know these specific commands will help us use the database system effectively and efficiently. In this practical, we will introduce more SQL*Plus and SQL commands in Oracle. 1. Editing Commands in the Buffer In Practical 1, we created new tables in a database and inserted tuples/rows into the tables at the SQL command prompt (). If any errors were made, you had to retype the whole command, which wasted much time. You can, however, use a number of SQL*Plus commands to edit a command. If you end a command without a semicolon, but with an empty new line, the command goes into a buffer. You may execute the command in the buffer by either the command RUN or a single slash (/) You may also edit the command in the buffer before you execute it. Here are some useful editing commands, see figure 1. They are shown in upper case, but may be either upper or lower. COMMAND APPEND text CHANGE /old/new CHANGE /text CLEAR BUFFER DEL ABBREVIATION A text C / old / new C /text CL BUFF (none) PURPOSE Add text at the end of the line Change old to new in a line Delete text from a line Delete all lines Delete a line 2

3 INPUT INPUT text LIST LIST n LIST * LIST LAST LIST m n I I text L L n or n L * L LAST L m n Add one or more lines Add a line consisting of text List all lines in SQL buffer List one line with line number n List the current line List the last line List a range of lines (m to n) Figure 1. SQL*Plus Editing Commands Try the following example to see how to use the SQL*Plus editing commands to edit the commands in the buffer. Now enter the query SELECT employeename, city 2 FROM employee WHERE city='harrison'; [NOTE: SQL command SELECT is for retrieve data or information from a database. The basic syntax of SELECT command is as follow: SELECT <columnlist> FROM <tablename> [WHERE <condition(s)>] < > means you have to provide the information to this item, [ ] means the item is optional. ] To edit this command, firstly you can use LIST command to see the whole command list 1 select employeename, city 2* from employee where city='harrison' The semicolon(;) is used to mark the end of a command and it is not put into the buffer. This means a new line can be added to the end of the buffer without removing the semicolon from the line that was previously the last. Any editing command other than LIST, affects only a single line in the buffer. This line called the current line. It is marked with an asterisk when you list the current command. Try the following commands at the prompt: list 2; Now use the change /old/new command to edit the second line. The / or RUN command after the SQL prompt (>) is used to return and execute the command stored in the buffer. list 2 2* from employee where city='harrison' change /city/employeename 2* from employee where employeename='harrison' change /Harrison/Jones 3

4 2* from employee where employeename='jones' / EMPLOYEENAME CITY Jones Harrison Appending and Deleting a Line By combining the INPUT, APPEND and DEL commands, you can manipulate commands further. Firstly, type in the following two lines of the query followed by two continuous ENTER strokes. These two command lines will be stored in the buffer: select employeename 2* from works 3 To add an extra line, use the INPUT command and then add the line where salary < i 3 where salary < Use the RUN (or /) or LIST, RUN command to test the query. The DEL command will delete a line or whatever line number you choose. Delete the last line and use INPUT to write where salary >. APPEND will add to a line, so you can complete line 3 by entering APPEND Try it and re-run the query. 2. Batch execution of SQL commands Whatever the above SQL*Plus editing commands we can use, the SQL*Plus editor is a line editor which is not fun. The user does not have control over the screen. Line editors do not allow a user to move the cursor up and down, and clicking with a mouse is definitely out of the question. To avoid these problems, you can use alternative ways to editor and execute SQL commands in a batch. Two recommended ways are listed here: i) Using another text editor. You can use another text editor such as Notepad or any other text editor in Windows to type your SQL commands. Within the text editor, you can do fullscreen editing. The SQL command typed in a full-screen text editor can be copied to the clipboard, and then pasted into SQL*Plus to execute it at the prompt. 4

5 Exercise: Open the text editor Notepad from your computer, type in the following SQL command within Notepad: SELECT employeename FROM works WHERE salary > 15000; Make changes to the typos. Copy this command, paste it at the prompt, and then execute it. ii) Edit and execute a SQL command file. If you are now using a computer in a Deakin lab, you can use a text editor such as Notepad or any other text editor in Windows to type your SQL commands, and then save them in a file with a.sql extension on your H: drive. At the prompt, type a command in the following format to execute the SQL commands in the saved.sql file: Exercise: Open the text editor Notepad from your computer, type in the following SQL commands within Notepad: CREATE TABLE staff (staffname CHAR(15) NOT NULL, street CHAR(15), city CHAR(10), PRIMARY KEY (staffname)); INSERT INTO staff VALUES ('David', 'Huntingdale', 'Whitehorse'); INSERT INTO staff VALUES ('Harry', 'Main', 'Kew'); INSERT INTO staff VALUES ('Mary', 'Cliffton', 'Monash'); Save these commands in the file ex1.sql on your H: drive, and then Check your database to see whether table staff exists: List the data in table staff: SELECT table_name FROM user_tables 2 WHERE table_name = STAFF ; SELECT * FROM staff; [Note: It can be seen that you can type in many SQL commands in a.sql file, and execute these command in a batch, instead of executing them one by one.] 5

6 If you are now using your home computer, you can use a text editor such as Notepad or any other text editor in Windows to type your SQL commands, save them in a file with a.sql extension on your home computer, then upload the sql file to your H: drive on the Deakin server (interactive.deakin.edu.au). The execution of the sql file is the same as above. You can use any FTP software such as WS_FTP to upload your sql file to your H: drive on the Deakin server. The WS_FTP software can be downloaded from the following Deakin software website: After installing and launching the WS_FTP, connect to the Deakin server using your Deakin username and password like this: Click OK to connect to the server (interactive.deakin.edu.au). When the connection is successful, the WS_FTP interface looks like this (yours might be a little bit different): 6

7 then select the sql file you are going to upload from your local computer (left side), then upload ( >) it to your H: drive (the / on the Remote Site within the WS_FTP interface means your H: drive) on the Deakin server (right side). Exercise: Do the above exercise by saving the commands in the file ex1.sql on your home computer, upload it to your H: drive on the Deakin server, and then execute the file as above. 3. Help Facilities At the SQL > prompt, type help followed by a keyword or sequence of keywords that are used together in SQL commands, for example, help select or help create table If you are lucky, the keyword or phrase will be among those for which help exists, and you will get a (somewhat) helpful message, usually ending in an example or two. Sometimes, the results of a SQL command execution may be too long to display on a screen. If so, you can issue SQL > set pause on to activate the paging feature. When this feature is activated, output will pause at the end of each screen until you hit the "Return" key. You can try the above commands again under this setting to see the effect. To turn this feature off, execute SQL > set pause off 7