diff options
Diffstat (limited to 'doc/src/sgml/start.sgml')
| -rw-r--r-- | doc/src/sgml/start.sgml | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/doc/src/sgml/start.sgml b/doc/src/sgml/start.sgml new file mode 100644 index 0000000..2a47f69 --- /dev/null +++ b/doc/src/sgml/start.sgml @@ -0,0 +1,410 @@ +<!-- doc/src/sgml/start.sgml --> + + <chapter id="tutorial-start"> + <title>Getting Started</title> + + <sect1 id="tutorial-install"> + <title>Installation</title> + + <para> + Before you can use <productname>PostgreSQL</productname> you need + to install it, of course. It is possible that + <productname>PostgreSQL</productname> is already installed at your + site, either because it was included in your operating system + distribution or because the system administrator already installed + it. If that is the case, you should obtain information from the + operating system documentation or your system administrator about + how to access <productname>PostgreSQL</productname>. + </para> + + <para> + If you are not sure whether <productname>PostgreSQL</productname> + is already available or whether you can use it for your + experimentation then you can install it yourself. Doing so is not + hard and it can be a good exercise. + <productname>PostgreSQL</productname> can be installed by any + unprivileged user; no superuser (<systemitem>root</systemitem>) + access is required. + </para> + + <para> + If you are installing <productname>PostgreSQL</productname> + yourself, then refer to <xref linkend="installation"/> + for instructions on installation, and return to + this guide when the installation is complete. Be sure to follow + closely the section about setting up the appropriate environment + variables. + </para> + + <para> + If your site administrator has not set things up in the default + way, you might have some more work to do. For example, if the + database server machine is a remote machine, you will need to set + the <envar>PGHOST</envar> environment variable to the name of the + database server machine. The environment variable + <envar>PGPORT</envar> might also have to be set. The bottom line is + this: if you try to start an application program and it complains + that it cannot connect to the database, you should consult your + site administrator or, if that is you, the documentation to make + sure that your environment is properly set up. If you did not + understand the preceding paragraph then read the next section. + </para> + </sect1> + + + <sect1 id="tutorial-arch"> + <title>Architectural Fundamentals</title> + + <para> + Before we proceed, you should understand the basic + <productname>PostgreSQL</productname> system architecture. + Understanding how the parts of + <productname>PostgreSQL</productname> interact will make this + chapter somewhat clearer. + </para> + + <para> + In database jargon, <productname>PostgreSQL</productname> uses a + client/server model. A <productname>PostgreSQL</productname> + session consists of the following cooperating processes + (programs): + + <itemizedlist> + <listitem> + <para> + A server process, which manages the database files, accepts + connections to the database from client applications, and + performs database actions on behalf of the clients. The + database server program is called + <filename>postgres</filename>. + <indexterm><primary>postgres</primary></indexterm> + </para> + </listitem> + + <listitem> + <para> + The user's client (frontend) application that wants to perform + database operations. Client applications can be very diverse + in nature: a client could be a text-oriented tool, a graphical + application, a web server that accesses the database to + display web pages, or a specialized database maintenance tool. + Some client applications are supplied with the + <productname>PostgreSQL</productname> distribution; most are + developed by users. + </para> + </listitem> + + </itemizedlist> + </para> + + <para> + As is typical of client/server applications, the client and the + server can be on different hosts. In that case they communicate + over a TCP/IP network connection. You should keep this in mind, + because the files that can be accessed on a client machine might + not be accessible (or might only be accessible using a different + file name) on the database server machine. + </para> + + <para> + The <productname>PostgreSQL</productname> server can handle + multiple concurrent connections from clients. To achieve this it + starts (<quote>forks</quote>) a new process for each connection. + From that point on, the client and the new server process + communicate without intervention by the original + <filename>postgres</filename> process. Thus, the + master server process is always running, waiting for + client connections, whereas client and associated server processes + come and go. (All of this is of course invisible to the user. We + only mention it here for completeness.) + </para> + </sect1> + + + <sect1 id="tutorial-createdb"> + <title>Creating a Database</title> + + <indexterm zone="tutorial-createdb"> + <primary>database</primary> + <secondary>creating</secondary> + </indexterm> + + <indexterm zone="tutorial-createdb"> + <primary>createdb</primary> + </indexterm> + + <para> + The first test to see whether you can access the database server + is to try to create a database. A running + <productname>PostgreSQL</productname> server can manage many + databases. Typically, a separate database is used for each + project or for each user. + </para> + + <para> + Possibly, your site administrator has already created a database + for your use. In that case you can omit this step and skip ahead + to the next section. + </para> + + <para> + To create a new database, in this example named + <literal>mydb</literal>, you use the following command: +<screen> +<prompt>$</prompt> <userinput>createdb mydb</userinput> +</screen> + If this produces no response then this step was successful and you can skip over the + remainder of this section. + </para> + + <para> + If you see a message similar to: +<screen> +createdb: command not found +</screen> + then <productname>PostgreSQL</productname> was not installed properly. Either it was not + installed at all or your shell's search path was not set to include it. + Try calling the command with an absolute path instead: +<screen> +<prompt>$</prompt> <userinput>/usr/local/pgsql/bin/createdb mydb</userinput> +</screen> + The path at your site might be different. Contact your site + administrator or check the installation instructions to + correct the situation. + </para> + + <para> + Another response could be this: +<screen> +createdb: could not connect to database postgres: could not connect to server: No such file or directory + Is the server running locally and accepting + connections on Unix domain socket "/tmp/.s.PGSQL.5432"? +</screen> + This means that the server was not started, or it was not started + where <command>createdb</command> expected it. Again, check the + installation instructions or consult the administrator. + </para> + + <para> + Another response could be this: +<screen> +createdb: could not connect to database postgres: FATAL: role "joe" does not exist +</screen> + where your own login name is mentioned. This will happen if the + administrator has not created a <productname>PostgreSQL</productname> user account + for you. (<productname>PostgreSQL</productname> user accounts are distinct from + operating system user accounts.) If you are the administrator, see + <xref linkend="user-manag"/> for help creating accounts. You will need to + become the operating system user under which <productname>PostgreSQL</productname> + was installed (usually <literal>postgres</literal>) to create the first user + account. It could also be that you were assigned a + <productname>PostgreSQL</productname> user name that is different from your + operating system user name; in that case you need to use the <option>-U</option> + switch or set the <envar>PGUSER</envar> environment variable to specify your + <productname>PostgreSQL</productname> user name. + </para> + + <para> + If you have a user account but it does not have the privileges required to + create a database, you will see the following: +<screen> +createdb: database creation failed: ERROR: permission denied to create database +</screen> + Not every user has authorization to create new databases. If + <productname>PostgreSQL</productname> refuses to create databases + for you then the site administrator needs to grant you permission + to create databases. Consult your site administrator if this + occurs. If you installed <productname>PostgreSQL</productname> + yourself then you should log in for the purposes of this tutorial + under the user account that you started the server as. + + <footnote> + <para> + As an explanation for why this works: + <productname>PostgreSQL</productname> user names are separate + from operating system user accounts. When you connect to a + database, you can choose what + <productname>PostgreSQL</productname> user name to connect as; + if you don't, it will default to the same name as your current + operating system account. As it happens, there will always be a + <productname>PostgreSQL</productname> user account that has the + same name as the operating system user that started the server, + and it also happens that that user always has permission to + create databases. Instead of logging in as that user you can + also specify the <option>-U</option> option everywhere to select + a <productname>PostgreSQL</productname> user name to connect as. + </para> + </footnote> + </para> + + <para> + You can also create databases with other names. + <productname>PostgreSQL</productname> allows you to create any + number of databases at a given site. Database names must have an + alphabetic first character and are limited to 63 bytes in + length. A convenient choice is to create a database with the same + name as your current user name. Many tools assume that database + name as the default, so it can save you some typing. To create + that database, simply type: +<screen> +<prompt>$</prompt> <userinput>createdb</userinput> +</screen> + </para> + + <para> + If you do not want to use your database anymore you can remove it. + For example, if you are the owner (creator) of the database + <literal>mydb</literal>, you can destroy it using the following + command: +<screen> +<prompt>$</prompt> <userinput>dropdb mydb</userinput> +</screen> + (For this command, the database name does not default to the user + account name. You always need to specify it.) This action + physically removes all files associated with the database and + cannot be undone, so this should only be done with a great deal of + forethought. + </para> + + <para> + More about <command>createdb</command> and <command>dropdb</command> can + be found in <xref linkend="app-createdb"/> and <xref linkend="app-dropdb"/> + respectively. + </para> + </sect1> + + + <sect1 id="tutorial-accessdb"> + <title>Accessing a Database</title> + + <indexterm zone="tutorial-accessdb"> + <primary>psql</primary> + </indexterm> + + <para> + Once you have created a database, you can access it by: + + <itemizedlist spacing="compact" mark="bullet"> + <listitem> + <para> + Running the <productname>PostgreSQL</productname> interactive + terminal program, called <application><firstterm>psql</firstterm></application>, which allows you + to interactively enter, edit, and execute + <acronym>SQL</acronym> commands. + </para> + </listitem> + + <listitem> + <para> + Using an existing graphical frontend tool like + <application>pgAdmin</application> or an office suite with + <acronym>ODBC</acronym> or <acronym>JDBC</acronym> support to create and manipulate a + database. These possibilities are not covered in this + tutorial. + </para> + </listitem> + + <listitem> + <para> + Writing a custom application, using one of the several + available language bindings. These possibilities are discussed + further in <xref linkend="client-interfaces"/>. + </para> + </listitem> + </itemizedlist> + + You probably want to start up <command>psql</command> to try + the examples in this tutorial. It can be activated for the + <literal>mydb</literal> database by typing the command: +<screen> +<prompt>$</prompt> <userinput>psql mydb</userinput> +</screen> + If you do not supply the database name then it will default to your + user account name. You already discovered this scheme in the + previous section using <command>createdb</command>. + </para> + + <para> + In <command>psql</command>, you will be greeted with the following + message: +<screen> +psql (&version;) +Type "help" for help. + +mydb=> +</screen> + <indexterm><primary>superuser</primary></indexterm> + The last line could also be: +<screen> +mydb=# +</screen> + That would mean you are a database superuser, which is most likely + the case if you installed the <productname>PostgreSQL</productname> instance + yourself. Being a superuser means that you are not subject to + access controls. For the purposes of this tutorial that is not + important. + </para> + + <para> + If you encounter problems starting <command>psql</command> + then go back to the previous section. The diagnostics of + <command>createdb</command> and <command>psql</command> are + similar, and if the former worked the latter should work as well. + </para> + + <para> + The last line printed out by <command>psql</command> is the + prompt, and it indicates that <command>psql</command> is listening + to you and that you can type <acronym>SQL</acronym> queries into a + work space maintained by <command>psql</command>. Try out these + commands: + <indexterm><primary>version</primary></indexterm> +<screen> +<prompt>mydb=></prompt> <userinput>SELECT version();</userinput> + version +-------------------------------------------------------------------&zwsp;----------------------- + PostgreSQL &version; on x86_64-pc-linux-gnu, compiled by gcc (Debian 4.9.2-10) 4.9.2, 64-bit +(1 row) + +<prompt>mydb=></prompt> <userinput>SELECT current_date;</userinput> + date +------------ + 2016-01-07 +(1 row) + +<prompt>mydb=></prompt> <userinput>SELECT 2 + 2;</userinput> + ?column? +---------- + 4 +(1 row) +</screen> + </para> + + <para> + The <command>psql</command> program has a number of internal + commands that are not SQL commands. They begin with the backslash + character, <quote><literal>\</literal></quote>. + For example, + you can get help on the syntax of various + <productname>PostgreSQL</productname> <acronym>SQL</acronym> + commands by typing: +<screen> +<prompt>mydb=></prompt> <userinput>\h</userinput> +</screen> + </para> + + <para> + To get out of <command>psql</command>, type: +<screen> +<prompt>mydb=></prompt> <userinput>\q</userinput> +</screen> + and <command>psql</command> will quit and return you to your + command shell. (For more internal commands, type + <literal>\?</literal> at the <command>psql</command> prompt.) The + full capabilities of <command>psql</command> are documented in + <xref linkend="app-psql"/>. In this tutorial we will not use these + features explicitly, but you can use them yourself when it is helpful. + </para> + + </sect1> + </chapter> |