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3rd chunk of `doc/src/sgml/func.sgml`
e9f44b8c70dc9df1a0d554fafc2007fcf95896cd68a3baec0000000100000fa1
   <entry>Operator</entry>
       <entry>Description</entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>&lt;</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Less than</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>&gt;</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Greater than</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>&lt;=</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Less than or equal to</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>&gt;=</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Greater than or equal to</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>=</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Equal</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>&lt;&gt;</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Not equal</entry>
      </row>

      <row>
       <entry>
        <replaceable>datatype</replaceable> <literal>!=</literal> <replaceable>datatype</replaceable>
        <returnvalue>boolean</returnvalue>
       </entry>
       <entry>Not equal</entry>
      </row>
     </tbody>
    </tgroup>
   </table>

   <note>
    <para>
     <literal>&lt;&gt;</literal> is the standard SQL notation for <quote>not
     equal</quote>.  <literal>!=</literal> is an alias, which is converted
     to <literal>&lt;&gt;</literal> at a very early stage of parsing.
     Hence, it is not possible to implement <literal>!=</literal>
     and <literal>&lt;&gt;</literal> operators that do different things.
    </para>
   </note>

   <para>
    These comparison operators are available for all built-in data types
    that have a natural ordering, including numeric, string, and date/time
    types.  In addition, arrays, composite types, and ranges can be compared
    if their component data types are comparable.
   </para>

   <para>
    It is usually possible to compare values of related data
    types as well; for example <type>integer</type> <literal>&gt;</literal>
    <type>bigint</type> will work.  Some cases of this sort are implemented
    directly by <quote>cross-type</quote> comparison operators, but if no
    such operator is available, the parser will coerce the less-general type
    to the more-general type and apply the latter's comparison operator.
   </para>

   <para>
    As shown above, all comparison operators are binary operators that
    return values of type <type>boolean</type>.  Thus, expressions like
    <literal>1 &lt; 2 &lt; 3</literal> are not valid (because there is
    no <literal>&lt;</literal> operator to compare a Boolean value with
    <literal>3</literal>).  Use the <literal>BETWEEN</literal> predicates
    shown below to perform range tests.
   </para>

   <para>
    There are also some comparison predicates, as shown in <xref
    linkend="functions-comparison-pred-table"/>.  These behave much like
    operators, but have special syntax mandated by the SQL standard.
   </para>

   <table id="functions-comparison-pred-table">
    <title>Comparison Predicates</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Predicate
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>
Title: Comparison Operators in PostgreSQL (Continued)
Summary
This section details the standard comparison operators in PostgreSQL, including <, >, <=, >=, =, <>, and !=, emphasizing that != is merely an alias for <>. It mentions that these operators are applicable to built-in data types with natural ordering (numeric, string, date/time) and composite types. It clarifies that comparisons between related data types (e.g., integer > bigint) are generally possible, either through cross-type operators or by coercing the less-general type. It highlights that all comparison operators return boolean values and that expressions like 1 < 2 < 3 are invalid. Finally, it introduces comparison predicates with special syntax.