GettingStartedWithOracle

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 Leland Systems Sun Solaris machines. These machines include elaine, epic, saga, myth, fable, tree, and cardinal.

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

    source /afs/ir/class/cs145/all.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.

Note that SQL is completely case-insensitive. Once you are in sqlplus, you can use capitals or not in keywords like ALTER; Even your password is case insensitive. We tend to capitalize keywords and not other things.

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)
    );

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.

Creating a Table With a Primary Key

To create a table that declares attribute a to be a primary key:

    CREATE TABLE <tableName> (..., a <type> PRIMARY KEY, b, ...);

To create a table that declares the set of attributes (a,b,c) to be a primary key:

    CREATE TABLE <tableName> (<attrs and their types>, PRIMARY KEY (a,b,c));

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.

To run the file foo.sql, type:

    @foo

sqlplus assumes by default the file extension ".sql" if there is no extension. So you could have entered @foo.sql at the SQL> prompt, but if you wanted to execute the file bar.txt, you would have to enter @bar.txt.

You can also run a file at connection by using a special form on the Unix command line. 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.

NOTE: If you are getting an error of the form "Input truncated to 2 characters" when you try to run your file, try putting an empty line at the bottom of your .sql file. This seems to make the error go away.

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.

LIST lists the command buffer, and makes the last line in the buffer the "current" line LIST n prints line n of the command buffer, and makes line n the current line LIST m n prints lines m through n, and makes line n the current line INPUT 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" CHANGE /old/new replaces the text "old" by "new" in the current line APPEND text appends "text" to the end of the current line DEL deletes the current line

All of these commands may be executed by entering the first letter or any other prefix of the command except for the DEL command.

An alternative is to edit the file where your SQL is kept directly from sqlplus. If you say

    edit foo.sql

the file foo.sql will be passed to an editor of your choice. The default is vi. However, you may say

    DEFINE _EDITOR = "emacs"

if you prefer to use the emacs editor; other editor choices may be called for in the analogous way. In fact, if you would like to make emacs your default editor, there is a login file that you may create in the directory from which you call sqlplus. Put in the file called login.sql the above editor-defining command, or any other commands you would like executed every time you call sqlplus.

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 on how to run the script command, check out its man page.

sqlplus provides the command spool to save query results to a file. At the SQL> prompt, you say:

   spool foo;

and a file called foo.lst will appear in your current directory and will record all user input and system output, until you exit sqlplus or type:

   spool off;

Note that if the file foo.lst existed previously, it will be overwritten, not appended.

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

In response to the SQL> prompt, type help followed by a keyword or sequence of keywords that are used together in SQL commands (e.g., help select and help create table both work). 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.

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;

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