</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

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

</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

</title>

<para>

GROUP BY specifies a grouped table derived by the application

ofthethis 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>

</programlisting></para>

<para>

Thecolumns in the ORDER BYmust appear in the SELECT clause.

Thus the following statement isillegal:

From release 6.4 of PostgreSQL, thecolumns in the ORDER BYclause do not need to appear in the SELECT clause.

Thus the following statement isnow legal:

<programlisting>

SELECT name FROM distributors ORDER BY code;

</programlisting></para>

</programlisting>

<para>

To sum the column <literal>len</literal> of all films and group

thereults by <literal>kind</literal>:

theresults by <literal>kind</literal>:

</para>

<programlisting>

SELECT kind, SUM(len) AS total FROM films GROUP BY kind;

<para>

To sum the column <literal>len</literal> of all films, group

thereults by <literal>kind</literal> and show those group totals

theresults by <literal>kind</literal> and show those group totals

that are less than 5 hours:

</para>

<programlisting>

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">