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<chapter id="queries">

<title>Queries</title>

<literal>DESC</> order, and <literal>NULLS LAST</> otherwise.

</para>

<para>

Note that the ordering options are considered independently for each

sort column. For example <literal>ORDER BY x, y DESC</> means

<literal>ORDER BY x ASC, y DESC</>, which is not the same as

<literal>ORDER BY x DESC, y DESC</>.

</para>

<para>

For backwards compatibility with the SQL92 version of the standard,

a <replaceable>sort_expression</> can instead be the name or number

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PostgreSQL documentation

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<synopsis>

ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...]

</synopsis>

<replaceable class="parameter">expression</replaceable> can be the

name or ordinal number of an output column

(<command>SELECT</command> list item), or it can be an arbitrary

expression formed from input-column values.

</para>

<para>

The <literal>ORDER BY</literal> clause causes the result rows to

be sorted according to the specified expression(s). If two rows are

equal according to the leftmost expression, they are compared

an implementation-dependent order.

</para>

<para>

Each <replaceable class="parameter">expression</replaceable> can be the

name or ordinal number of an output column

(<command>SELECT</command> list item), or it can be an arbitrary

expression formed from input-column values.

</para>

<para>

The ordinal number refers to the ordinal (left-to-right) position

of the result column. This feature makes it possible to define an

on whether the operator is a less-than or greater-than operator.

</para>

<para>

Note that ordering options apply only to the expression they follow;

for example <literal>ORDER BY x, y DESC</> does not mean

the same thing as <literal>ORDER BY x DESC, y DESC</>.

</para>

<para>

Character-string data is sorted according to the locale-specific

collation order that was established when the database cluster