Yurttas/PL/DBL/oracle/F/R/or-intro.html

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Getting Started With Oracle  ----

---- Overview

You will be using the Oracle database system to implement your PDA (Personal Database Application) this quarter. Important: As soon as your Oracle account is set up, you should log in to change the initial password.

---- Logging In to Oracle

You should be logged onto one of the Sun Solaris machines at L&IR. These machines include elaine, epic, saga, adelbert, tree, and cardinal.

Before using Oracle, execute the following line in your shell to set up the correct environment variables: 

     source /usr/class/cs145/cora.env

You may wish to put this line in your shell initialization file instead (for example, .cshrc).

Now, you can log in to Oracle by typing: 

     sqlplus <yourName>

Here, sqlplus is Oracle's generic SQL interface. <yourName> refers to your leland login.

You will be prompted for your password. This password is initially dbpasswd and must be changed as soon as possible. For security reasons, we suggest that you not use your regular leland password, because as we shall see there are opportunities for this password to become visible under certain circumstances. After you enter the correct password, you should receive the prompt 

     SQL>

---- Changing Your Password

In response to the SQL> prompt, type 

     alter user <yourName> identified by <newPassword>;

where <yourName> is again your leland login, and <newPassword> is the password you would like to use in the future. This command, like all other SQL commands, should be terminated with a semicolon.

---- Creating a Table

In sqlplus we can execute any SQL command. One simple type of command creates a table (relation). The form is 

     CREATE TABLE <tableName> (
         <list of attributes and their types>
     );

You may enter text on one line or on several lines. If your command runs over several lines, you will be prompted with line numbers until you type the semicolon that ends any command. (Warning: An empty line terminates the command but does not execute it; see Editing Commands in the Buffer.) An example table-creation command is: 

     create table test (
         i int,
         s char(10)
     );

Note that SQL is case insensitive, so CREATE TABLE TEST and create table test are the same. This command creates a table named test with two attributes. The first, named i, is an integer, and the second, named s, is a character string of length (up to) 10.

---- Inserting Tuples

Having created a table, we can insert tuples into it. The simplest way to insert is with the INSERT command: 

     INSERT INTO <tableName>
         VALUES( <list of values for attributes, in order> );

For instance, we can insert the tuple (10, 'foobar') into relation test by 

     INSERT INTO test VALUES(10, 'foobar');

---- Getting the Value of a Relation

We can see the tuples in a relation with the command: 

     SELECT *
     FROM <tableName>;

For instance, after the above create and insert statements, the command 

     SELECT * FROM test;

produces the result 

              I S
     ---------- ----------
             10 foobar

---- Getting Rid of Your Tables

To remove a table from your database, execute 

     DROP TABLE <tableName>;

We suggest you execute 

     DROP TABLE test;

after trying out this sequence of commands to avoid leaving a lot of garbage around that will be still there the next time you use the Oracle system.

---- Getting Information About Your Database

The system keeps information about your own database in certain system tables. The most important for now is USER_TABLES. You can recall the names of your tables by issuing the query: 

     SELECT TABLE_NAME
     FROM USER_TABLES;

More information about your tables is available from USER_TABLES. To see all the attributes of USER_TABLES, try: 

     SELECT *
     FROM USER_TABLES;

It is also possible to recall the attributes of a table once you know its name. Issue the command: 

     DESCRIBE <tableName>;

to learn about the attributes of relation <tableName>.

---- Quitting sqlplus

To leave sqlplus, type 

     quit;

in response to the SQL> prompt.

---- Executing SQL From a File

Instead of executing SQL commands typed at a terminal, it is often more convenient to type the SQL command(s) into a file and cause the file to be executed. There are two ways to do so.

The first is to provide your password and the name of the file in the command line with which you open sqlplus. The form of the command is: 

     sqlplus <yourName>/<yourPassword> @<fileName>

For instance, if user sally, whose password is etaoinshrdlu, wishes to execute the file foo.sql, then she would say: 

     sqlplus sally/etaoinshrdlu @foo

Notice that this mode presents a risk that sally's password will be discovered, so it should be used carefully. Also note that since sally did not specify an extension for the file name "foo",  sqlplus implicitly assumes the default extension ".sql". Therefore, it is a good idea to give every command file an extension, and specify the complete file name with the extension after the "@".

A second, safer way, is for sally to log in to sqlplus as usual. She then types, in response to the SQL> prompt: 

     @foo.sql

and the file foo.sql's contents will be executed.

---- Editing Commands in the Buffer

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. They are shown in upper case but may be either upper or lower.

L lists the command buffer, and makes the last line in the buffer the "current" line
L n prints line n of the command buffer, and makes line n the current line
L m n prints lines m through n, and makes line n the current line
I enters a mode that allows you to input text following the current line; you must terminate the sequence of new lines with a pair of "returns"
C /old/new replaces the text "old" by "new" in the current line
A text appends "text" to the end of the current line
DEL deletes the current line

===---- Recording Your Session===

There are several methods for creating a typescript to turn in for your programming assignments. The most primitive way is to cut and paste your terminal output and save it in a file (if you have windowing capabilities). Another method is to use the Unix command script to record the terminal interaction. The script command records everything printed on your screen. The syntax for the command is 

    script [ -a ] [ filename ]

The record is written to filename. If no file name is given, the record is saved in the file typescript. The -a option allows you to append the session record to filename, rather than overwrite it. To end the recording, type 

    exit

For more information about script, check out its man page.

Alternatively, you can use the spool command within sqlplus. At the SQL> prompt, you say: 

    spool foo;

and a file called foo.lst will appear in your current directory and will hold everything typed, until you exit sqlplus or type: 

    spool off;

Finally, if you use Emacs, you can simply run sqlplus in a shell buffer and save the buffer to a file. To prevent your Oracle password from being echoed in the Emacs buffer, add the following lines to your .emacs file: 

(setq-default
 comint-output-filter-functions
 '(comint-watch-for-password-prompt))
(setq
 comint-password-prompt-regexp
 "\\(\\([Oo]ld \\|[Nn]ew \\|^\\)[Pp]assword\\|Enter password\\):\\s *\\'")

---- Help Facilities and Other Hints

In response to the SQL> prompt, type help followed by a keyword. If you are lucky, the keyword will be one of those for which help exists, and you will get a (somewhat) helpful message, usually ending in an example or two. To see all the possible commands, for each of which help is available, type 

    help commands;

The output from help, and in general, the results of many SQL commands, can be too long to display on a screen. You can use 

    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. To turn this feature off, use 

    set pause off;

This document was written originally for Prof. Jeff Ullman's CS145 class in Autumn, 1997; revised by Jun Yang for Prof. Jennifer Widom's CS145 class in Spring, 1998.

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