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More complete info from Oliver Elphick.

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Thomas G. Lockhart 1999-02-13 03:32:43 +00:00
parent ad4b27ac3f
commit b106421473
2 changed files with 33 additions and 12 deletions
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6
doc/src/sgml/ref/copy.sgml
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@ -395,7 +395,11 @@ has the termination sequence on the last line):
</refsect1>
<refsect1 ID="R1-SQL-COPY-5">
<title>Bugs</title>
<title>Bugs and features</title>
<para>
<command>COPY</command> neither invokes rules nor acts on column defaults.
It does invoke triggers, however.
</para>
<para>
<command>COPY</command> stops operation at the first error. This
should not lead to problems in the event of

39
doc/src/sgml/ref/select.sgml
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@ -205,9 +205,15 @@ SELECT [ALL|DISTINCT [ON <replaceable class="PARAMETER">column</replaceable>] ]
Description
</title>
<para>
<command>SELECT</command> will get all rows which satisfy the
WHERE condition
or all rows of a table if WHERE is omitted.</para>
<command>SELECT</command> will return rows from one or more tables.
Candidates for selection are rows which satisfy the WHERE condition;
if WHERE is omitted, all rows are candidates.</para>
<para>
<command>DISTINCT</command> will eliminate all duplicate rows from the
selection.
<command>DISTINCT ON <replaceable class="PARAMETER">column</replaceable></command> will eliminate all duplicates in the specified column; this is
equivalent to using <command>GROUP BY <replaceable class="PARAMETER">column</replaceable></command>. <command>ALL</command> will return all candidate rows,
including duplicates.
<para>
The GROUP BY clause allows a user to divide a table
@ -247,8 +253,9 @@ WHERE <replaceable class="PARAMETER">expr</replaceable> <replaceable class="PARA
</synopsis>
where <replaceable class="PARAMETER">cond_op</replaceable> can be
one of: =, &lt;, &lt;=, &gt;, &gt;=, &lt;&gt;
or a conditional operator like ALL, ANY, IN, LIKE, et cetera
one of: =, &lt;, &lt;=, &gt;, &gt;= or &lt;&gt;,
a conditional operator like ALL, ANY, IN, LIKE, et cetera or a
locally-defined operator,
and <replaceable class="PARAMETER">log_op</replaceable> can be one
of: AND, OR, NOT.
The comparison returns either TRUE or FALSE and all
@ -266,10 +273,16 @@ WHERE <replaceable class="PARAMETER">expr</replaceable> <replaceable class="PARA
</title>
<para>
GROUP BY specifies a grouped table derived by the application
of the this clause:
of this clause:
<synopsis>
GROUP BY <replaceable class="PARAMETER">column</replaceable> [, ...]
</synopsis></para></refsect2>
</synopsis></para>
<para>
GROUP BY will condense into a single row all rows that share the same values for the
grouped columns; aggregates return values derived from all rows that make up the group. The value returned for an ungrouped
and unaggregated column is dependent on the order in which rows happen to be read from the database.
</para>
</refsect2>
<refsect2 id="R2-SQL-HAVING-2">
<refsect2info>
@ -327,8 +340,8 @@ SELECT title, date_prod + 1 AS newlen FROM films ORDER BY newlen;
</programlisting></para>
<para>
The columns in the ORDER BY must appear in the SELECT clause.
Thus the following statement is illegal:
From release 6.4 of PostgreSQL, the columns in the ORDER BY clause do not need to appear in the SELECT clause.
Thus the following statement is now legal:
<programlisting>
SELECT name FROM distributors ORDER BY code;
</programlisting></para>
@ -409,7 +422,7 @@ SELECT f.title, f.did, d.name, f.date_prod, f.kind
</programlisting>
<para>
To sum the column <literal>len</literal> of all films and group
the reults by <literal>kind</literal>:
the results by <literal>kind</literal>:
</para>
<programlisting>
SELECT kind, SUM(len) AS total FROM films GROUP BY kind;
@ -425,7 +438,7 @@ SELECT kind, SUM(len) AS total FROM films GROUP BY kind;
<para>
To sum the column <literal>len</literal> of all films, group
the reults by <literal>kind</literal> and show those group totals
the results by <literal>kind</literal> and show those group totals
that are less than 5 hours:
</para>
<programlisting>
@ -563,6 +576,10 @@ SELECT distributors.* WHERE name = 'Westwood';
This is not currently
allowed in <productname>Postgres</productname>.
</para>
<para>
The DISTINCT ON phrase is not part of <acronym>SQL92</acronym>.
</para>
</refsect3>
<refsect3 id="R3-SQL-UNION-1">