294 lines
9.9 KiB
Plaintext
294 lines
9.9 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/Attic/manage.sgml,v 1.13 2001/02/04 15:28:18 petere Exp $
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-->
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<Chapter Id="manage">
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<Title>Managing a Database</Title>
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<Note>
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<Para>
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This section is currently a thinly disguised copy of the
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Tutorial. Needs to be augmented.
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- thomas 1998-01-12
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</Para>
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</Note>
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<Para>
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Although the <FirstTerm>site administrator</FirstTerm> is responsible for overall management
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of the <ProductName>Postgres</ProductName> installation, some databases within the
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installation may be managed by another person,
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designated the <FirstTerm>database administrator</FirstTerm>.
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This assignment of responsibilities occurs when a database is created.
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A user may be assigned explicit privileges to create databases and/or to create new users.
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A user assigned both privileges can perform most administrative task
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within <ProductName>Postgres</ProductName>, but will
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not by default have the same operating system privileges as the site administrator.
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</Para>
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<Para>
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The Database Administrator's Guide covers these topics in more detail.
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</Para>
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<Sect1 id="db-creation">
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<Title>Database Creation</Title>
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<Para>
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Databases are created by the <Command>create database</Command> issued from
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within <ProductName>Postgres</ProductName>. <Application>createdb</Application> is a command-line
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utility provided to give the same functionality from outside <ProductName>Postgres</ProductName>.
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</Para>
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<Para>
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The <ProductName>Postgres</ProductName> backend must be running for either method
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to succeed, and the user issuing the command must be the <ProductName>Postgres</ProductName>
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<FirstTerm>superuser</FirstTerm> or have been assigned database creation privileges by the
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superuser.
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</Para>
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<Para>
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To create a new database named <literal>mydb</literal> from the command line, type
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<ProgramListing>
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% createdb mydb
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</ProgramListing>
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and to do the same from within <Application>psql</Application> type
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<ProgramListing>
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=> CREATE DATABASE mydb;
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</ProgramListing>
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</Para>
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<Para>
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If you do not have the privileges required to create a database, you will see
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the following:
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<ProgramListing>
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ERROR: CREATE DATABASE: Permission denied.
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</ProgramListing>
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</Para>
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<Para>
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<ProductName>Postgres</ProductName> allows you to create any number of databases
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at a given site and you automatically become the
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database administrator of the database you just created.
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Database names must have an alphabetic first
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character and are limited to 32 characters in length.
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</Para>
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</Sect1>
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<Sect1 id="altern-locations">
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<Title>Alternate Database Locations</Title>
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<Para>
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It is possible to create a database in a location other than the default
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location for the installation. Remember that all database access actually
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occurs through the database backend, so that any location specified must
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be accessible by the backend.
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</Para>
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<Para>
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Alternate database locations are created and referenced by an environment variable
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which gives the absolute path to the intended storage location.
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This environment variable must have been defined before the postmaster was started
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and the location it points to must be writable by the postgres administrator account.
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Consult with the site administrator
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regarding preconfigured alternate database locations.
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Any valid environment variable name may be used to reference an alternate location,
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although using variable names with a prefix of <envar>PGDATA</envar> is recommended
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to avoid confusion
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and conflict with other variables.
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</Para>
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<Note>
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<Para>
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In previous versions of <ProductName>Postgres</ProductName>,
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it was also permissable to use an absolute path name to specify
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an alternate storage location.
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Although the environment variable style of specification
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is to be preferred since it allows the site administrator more flexibility in
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managing disk storage, it is also possible to use an absolute path
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to specify an alternate location.
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The administrator's guide discusses how to enable this feature.
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</Para>
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</Note>
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<Para>
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For security and integrity reasons,
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any path or environment variable specified has some
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additional path fields appended.
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Alternate database locations must be prepared by running
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<Application>initlocation</Application>.
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</Para>
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<Para>
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To create a data storage area using the environment variable
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<envar>PGDATA2</envar> (for this example set to <filename>/alt/postgres</filename>),
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ensure that <FileName>/alt/postgres</FileName> already exists and is writable by
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the Postgres administrator account.
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Then, from the command line, type
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<ProgramListing>
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% initlocation PGDATA2
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Creating Postgres database system directory /alt/postgres/data
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Creating Postgres database system directory /alt/postgres/data/base
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</ProgramListing>
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</Para>
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<Para>
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To create a database in the alternate storage area <envar>PGDATA2</envar>
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from the command line, use the following command:
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<ProgramListing>
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% createdb -D PGDATA2 mydb
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</ProgramListing>
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and to do the same from within <Application>psql</Application> type
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<ProgramListing>
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=> CREATE DATABASE mydb WITH LOCATION = 'PGDATA2';
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</ProgramListing>
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</Para>
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<Para>
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If you do not have the privileges required to create a database, you will see
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the following:
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<ProgramListing>
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ERROR: CREATE DATABASE: permission denied
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</ProgramListing>
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</Para>
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<Para>
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If the specified location does not exist or the database backend does not have
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permission to access it or to write to directories under it, you will see
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the following:
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<ProgramListing>
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ERROR: The database path '/no/where' is invalid. This may be due to a character that is not allowed or because the chosen path isn't permitted for databases.
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</ProgramListing>
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</Para>
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</Sect1>
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<Sect1 id="db-accessing">
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<Title>Accessing a Database</Title>
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<Para>
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Once you have constructed a database, you can access it
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by:
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<ItemizedList Mark="bullet" Spacing="compact">
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<ListItem>
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<Para>
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running the <ProductName>PostgreSQL</ProductName> interactive terminal
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<Application>psql</Application> which allows you to interactively
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enter, edit, and execute <Acronym>SQL</Acronym> commands.
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</Para>
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</ListItem>
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<ListItem>
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<Para>
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writing a C program using the LIBPQ subroutine
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library. This allows you to submit <Acronym>SQL</Acronym> commands
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from C and get answers and status messages back to
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your program. This interface is discussed further
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in <citetitle>The PostgreSQL Programmer's Guide</citetitle>.
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</Para>
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</ListItem>
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</ItemizedList>
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You might want to start up <Application>psql</Application>,
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to try out the examples in this manual.
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It can be activated for the <Database>mydb</Database>
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database by typing the command:
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<ProgramListing>
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% psql mydb
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</ProgramListing>
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You will be greeted with the following message:
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<ProgramListing>
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Welcome to psql, the PostgreSQL interactive terminal.
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Type: \copyright for distribution terms
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\h for help with SQL commands
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\? for help on internal slash commands
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\g or terminate with semicolon to execute query
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\q to quit
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mydb=>
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</ProgramListing>
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</Para>
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<Para>
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This prompt indicates that psql is listening
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to you and that you can type <Acronym>SQL</Acronym> queries into a
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workspace maintained by the terminal monitor.
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The <Application>psql</Application> program responds to escape codes that begin
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with the backslash character, "<literal>\</literal>". For example, you
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can get help on the syntax of various
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<ProductName>PostgreSQL</ProductName> <Acronym>SQL</Acronym> commands by typing:
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<ProgramListing>
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mydb=> \h
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</ProgramListing>
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Once you have finished entering your queries into the
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workspace, you can pass the contents of the workspace
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to the <ProductName>Postgres</ProductName> server by typing:
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<ProgramListing>
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mydb=> \g
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</ProgramListing>
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This tells the server to process the query. If you
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terminate your query with a semicolon, the "<literal>\g</literal>" is not
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necessary.
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<Application>psql</Application> will automatically process semicolon terminated queries.
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To read queries from a file, say myFile, instead of
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entering them interactively, type:
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<ProgramListing>
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mydb=> \i fileName
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</ProgramListing>
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To get out of <Application>psql</Application> and return to Unix, type
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<ProgramListing>
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mydb=> \q
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</ProgramListing>
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and <Application>psql</Application> will quit and return you to your command
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shell. (For more escape codes, type <Command>\?</Command> at the psql
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prompt.)
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White space (i.e., spaces, tabs and newlines) may be
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used freely in <Acronym>SQL</Acronym> queries. Single-line comments are denoted by
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"<literal>--</literal>". Everything after the dashes up to the end of the
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line is ignored. Multiple-line comments, and comments within a line,
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are denoted by "<literal>/* ... */</literal>".
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</Para>
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</Sect1>
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<Sect1 id="db-destroy">
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<Title>Destroying a Database</Title>
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<Para>
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If you are the owner of the database
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<Database>mydb</Database>, you can destroy it using the following Unix command:
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<ProgramListing>
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% dropdb mydb
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</ProgramListing>
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This action physically removes all of the Unix files
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associated with the database and cannot be undone, so
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this should only be done with a great deal of forethought.
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</Para>
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</Sect1>
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</Chapter>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode:sgml
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sgml-omittag:nil
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"./reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:("/usr/lib/sgml/catalog")
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sgml-local-ecat-files:nil
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End:
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-->
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