<para>

The right-hand side is a parenthesized list

ofscalarexpressions. The result is <quote>true</quote> if the left-hand expression's

of expressions. The result is <quote>true</quote> if the left-hand expression's

result is equal to any of the right-hand expressions. This is a shorthand

notation for

<para>

The right-hand side is a parenthesized list

ofscalarexpressions. The result is <quote>true</quote> if the left-hand expression's

of expressions. The result is <quote>true</quote> if the left-hand expression's

result is unequal to all of the right-hand expressions. This is a shorthand

notation for

<para>

Each side is a row constructor,

as described in <xref linkend="sql-syntax-row-constructors"/>.

The two row values must have the same number of fields.

Each side is evaluated and they are compared row-wise. Row constructor

comparisons are allowed when the <replaceable>operator</replaceable> is

The two row constructors must have the same number of fields.

The given <replaceable>operator</replaceable> is applied to each pair

of corresponding fields. (Since the fields could be of different

types, this means that a different specific operator could be selected

for each pair.)

All the selected operators must be members of some B-tree operator

class, or be the negator of an <literal>=</literal> member of a B-tree

operator class, meaning that row constructor comparison is only

possible when the <replaceable>operator</replaceable> is

<literal>=</literal>,

<literal>&lt;&gt;</literal>,

<literal>&lt;</literal>,

<literal>&lt;=</literal>,

<literal>&gt;</literal> or

<literal>&gt;=</literal>.

Every row element must be of a type which has a default B-tree operator

class or the attempted comparison may generate an error.

<literal>&gt;</literal>, or

<literal>&gt;=</literal>,

or has semantics similar to one of these.

</para>

<note>

<para>

Errors related to the number or types of elements might not occur if

the comparison is resolved using earlier columns.

</para>

</note>

<para>

The <literal>=</literal> and <literal>&lt;&gt;</literal> cases work slightly differently

from the others. Two rows are considered

considered.

</para>

<note>

<para>

Prior to <productname>PostgreSQL</productname> 8.2, the

<literal>&lt;</literal>, <literal>&lt;=</literal>, <literal>&gt;</literal> and <literal>&gt;=</literal>

cases were not handled per SQL specification. A comparison like

<literal>ROW(a,b) &lt; ROW(c,d)</literal>

was implemented as

<literal>a &lt; c AND b &lt; d</literal>

whereas the correct behavior is equivalent to

<literal>a &lt; c OR (a = c AND b &lt; d)</literal>.

</para>

</note>

<synopsis>

<replaceable>row_constructor</replaceable> IS DISTINCT FROM <replaceable>row_constructor</replaceable>

</synopsis>