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Some marginal editorial improvements and updates in the tutorial.

This commit is contained in:
Tom Lane 2006-10-21 23:12:57 +00:00
parent 9c2c41646a
commit ed19393326
3 changed files with 30 additions and 23 deletions
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4
doc/src/sgml/advanced.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/advanced.sgml,v 1.51 2006/09/16 00:30:11 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/advanced.sgml,v 1.52 2006/10/21 23:12:57 tgl Exp $ -->
<chapter id="tutorial-advanced">
<title>Advanced Features</title>
@ -384,7 +384,7 @@ CREATE TABLE capitals (
type of the column <structfield>name</structfield> is
<type>text</type>, a native <productname>PostgreSQL</productname>
type for variable length character strings. State capitals have
an extra column, state, that shows their state. In
an extra column, <structfield>state</>, that shows their state. In
<productname>PostgreSQL</productname>, a table can inherit from
zero or more other tables.
</para>

37
doc/src/sgml/query.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/query.sgml,v 1.47 2006/09/16 00:30:15 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/query.sgml,v 1.48 2006/10/21 23:12:57 tgl Exp $ -->
<chapter id="tutorial-sql">
<title>The <acronym>SQL</acronym> Language</title>
@ -20,7 +20,7 @@
<para>
In the examples that follow, we assume that you have created a
database named <literal>mydb</literal>, as described in the previous
chapter, and have started <application>psql</application>.
chapter, and have been able to start <application>psql</application>.
</para>
<para>
@ -35,12 +35,15 @@
</screen>
This creates the scripts and compiles the C files containing user-defined
functions and types. (You must use GNU make for this &mdash; it may be named
something different on your system, often <application>gmake</>.)
functions and types. (If you installed a pre-packaged version of
<productname>PostgreSQL</productname> rather than building from source,
look for a directory named <filename>tutorial</> within the
<productname>PostgreSQL</productname> documentation. The <quote>make</>
part should already have been done for you.)
Then, to start the tutorial, do the following:
<screen>
<prompt>$</prompt> <userinput>cd <replaceable>....</replaceable>/src/tutorial</userinput>
<prompt>$</prompt> <userinput>cd <replaceable>....</replaceable>/tutorial</userinput>
<prompt>$</prompt> <userinput>psql -s mydb</userinput>
<computeroutput>
...
@ -416,7 +419,7 @@ SELECT DISTINCT city
In some database systems, including older versions of
<productname>PostgreSQL</productname>, the implementation of
<literal>DISTINCT</literal> automatically orders the rows and
so <literal>ORDER BY</literal> is redundant. But this is not
so <literal>ORDER BY</literal> is unnecessary. But this is not
required by the SQL standard, and current
<productname>PostgreSQL</productname> doesn't guarantee that
<literal>DISTINCT</literal> causes the rows to be ordered.
@ -518,8 +521,10 @@ SELECT city, temp_lo, temp_hi, prcp, date, location
<para>
Since the columns all had different names, the parser
automatically found out which table they belong to, but it is good
style to fully qualify column names in join queries:
automatically found out which table they belong to. If there
were duplicate column names in the two tables you'd need to
<firstterm>qualify</> the column names to show which one you
meant, as in:
<programlisting>
SELECT weather.city, weather.temp_lo, weather.temp_hi,
@ -527,6 +532,10 @@ SELECT weather.city, weather.temp_lo, weather.temp_hi,
FROM weather, cities
WHERE cities.name = weather.city;
</programlisting>
It is widely considered good style to qualify all column names
in a join query, so that the query won't fail if a duplicate
column name is later added to one of the tables.
</para>
<para>
@ -548,7 +557,7 @@ SELECT *
Now we will figure out how we can get the Hayward records back in.
What we want the query to do is to scan the
<classname>weather</classname> table and for each row to find the
matching <classname>cities</classname> row. If no matching row is
matching <classname>cities</classname> row(s). If no matching row is
found we want some <quote>empty values</quote> to be substituted
for the <classname>cities</classname> table's columns. This kind
of query is called an <firstterm>outer join</firstterm>. (The
@ -681,11 +690,11 @@ SELECT city FROM weather WHERE temp_lo = max(temp_lo); <lineannotation>WRONG
but this will not work since the aggregate
<function>max</function> cannot be used in the
<literal>WHERE</literal> clause. (This restriction exists because
the <literal>WHERE</literal> clause determines the rows that will
go into the aggregation stage; so it has to be evaluated before
aggregate functions are computed.)
the <literal>WHERE</literal> clause determines which rows will be
included in the aggregate calculation; so obviously it has to be evaluated
before aggregate functions are computed.)
However, as is often the case
the query can be restated to accomplish the intended result, here
the query can be restated to accomplish the desired result, here
by using a <firstterm>subquery</firstterm>:
<programlisting>
@ -808,7 +817,7 @@ SELECT city, max(temp_lo)
You can update existing rows using the
<command>UPDATE</command> command.
Suppose you discover the temperature readings are
all off by 2 degrees as of November 28. You may update the
all off by 2 degrees after November 28. You may correct the
data as follows:
<programlisting>

12
doc/src/sgml/start.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/start.sgml,v 1.42 2006/09/16 00:30:15 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/start.sgml,v 1.43 2006/10/21 23:12:57 tgl Exp $ -->
<chapter id="tutorial-start">
<title>Getting Started</title>
@ -181,8 +181,7 @@ createdb: command not found
<para>
Another response could be this:
<screen>
createdb: could not connect to database postgres: could not connect to server:
No such file or directory
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>
@ -194,8 +193,7 @@ No such file or directory
<para>
Another response could be this:
<screen>
createdb: could not connect to database postgres: FATAL: user "joe" does not
exist
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</> user account
@ -229,7 +227,7 @@ createdb: database creation failed: ERROR: permission denied to create database
<para>
As an explanation for why this works:
<productname>PostgreSQL</productname> user names are separate
from operating system user accounts. If you connect to a
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
@ -353,7 +351,7 @@ mydb=#
That would mean you are a database superuser, which is most likely
the case if you installed <productname>PostgreSQL</productname>
yourself. Being a superuser means that you are not subject to
access controls. For the purpose of this tutorial this is not of
access controls. For the purposes of this tutorial that is not of
importance.
</para>