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>Chapter 6. Functions and Operators</TD
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><DIV
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><H1
CLASS="SECT1"
><A
NAME="FUNCTIONS-BINARYSTRING"
>6.5. Binary String Functions and Operators</A
></H1
><P
>    This section describes functions and operators for examining and
    manipulating binary string values.  Strings in this context mean
    values of the type <TT
CLASS="TYPE"
>BYTEA</TT
>.
   </P
><P
>    <SPAN
CLASS="ACRONYM"
>SQL</SPAN
> defines some string functions with a
    special syntax where 
    certain key words rather than commas are used to separate the
    arguments.  Details are in
    <A
HREF="functions-binarystring.html#FUNCTIONS-BINARYSTRING-SQL"
>Table 6-9</A
>.
    Some functions are also implemented using the regular syntax for
    function invocation.
    (See <A
HREF="functions-binarystring.html#FUNCTIONS-BINARYSTRING-OTHER"
>Table 6-10</A
>.)
   </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-BINARYSTRING-SQL"
></A
><P
><B
>Table 6-9. <SPAN
CLASS="ACRONYM"
>SQL</SPAN
> Binary String Functions and Operators</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Function</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Return Type</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Description</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Example</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Result</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> <TT
CLASS="PARAMETER"
><I
>string</I
></TT
> <TT
CLASS="LITERAL"
>||</TT
>
        <TT
CLASS="PARAMETER"
><I
>string</I
></TT
> </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> <TT
CLASS="TYPE"
>bytea</TT
> </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        String concatenation
        <A
NAME="AEN7133"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>'\\\\Post'::bytea || '\\047greSQL\\000'::bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>\\Post'greSQL\000</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>octet_length</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Number of bytes in binary string</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>octet_length('jo\\000se'::bytea)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>5</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>position</TT
>(<TT
CLASS="PARAMETER"
><I
>substring</I
></TT
> in <TT
CLASS="PARAMETER"
><I
>string</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Location of specified substring</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>position('\\000om'::bytea in 'Th\\000omas'::bytea)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>3</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>substring</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
> [<SPAN
CLASS="OPTIONAL"
>from <TT
CLASS="TYPE"
>integer</TT
></SPAN
>] [<SPAN
CLASS="OPTIONAL"
>for <TT
CLASS="TYPE"
>integer</TT
></SPAN
>])</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Extract substring
        <A
NAME="AEN7174"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>substring('Th\\000omas'::bytea from 2 for 3)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>h\000o</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        <TT
CLASS="FUNCTION"
>trim</TT
>([<SPAN
CLASS="OPTIONAL"
>both</SPAN
>]
        <TT
CLASS="PARAMETER"
><I
>characters</I
></TT
> from
        <TT
CLASS="PARAMETER"
><I
>string</I
></TT
>)
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Remove the longest string containing only the
        <TT
CLASS="PARAMETER"
><I
>characters</I
></TT
> from the
        beginning/end/both ends of the <TT
CLASS="PARAMETER"
><I
>string</I
></TT
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>trim('\\000'::bytea from '\\000Tom\\000'::bytea)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>Tom</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>get_byte</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>, <TT
CLASS="PARAMETER"
><I
>offset</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Extract byte from string.
        <A
NAME="AEN7203"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>get_byte('Th\\000omas'::bytea, 4)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>109</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>set_byte</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>,
       <TT
CLASS="PARAMETER"
><I
>offset</I
></TT
>, <TT
CLASS="PARAMETER"
><I
>newvalue</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Set byte in string.
        <A
NAME="AEN7218"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>set_byte('Th\\000omas'::bytea, 4, 64)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>Th\000o@as</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>get_bit</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>, <TT
CLASS="PARAMETER"
><I
>offset</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Extract bit from string.
        <A
NAME="AEN7232"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>get_bit('Th\\000omas'::bytea, 45)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>1</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>set_bit</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>,
       <TT
CLASS="PARAMETER"
><I
>offset</I
></TT
>, <TT
CLASS="PARAMETER"
><I
>newvalue</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Set bit in string.
        <A
NAME="AEN7247"
></A
>
       </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>set_bit('Th\\000omas'::bytea, 45, 0)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>Th\000omAs</TT
></TD
></TR
></TBODY
></TABLE
></DIV
><P
>    Additional binary string manipulation functions are available and
    are listed in <A
HREF="functions-binarystring.html#FUNCTIONS-BINARYSTRING-OTHER"
>Table 6-10</A
>.  Some
    of them are used internally to implement the
    <SPAN
CLASS="ACRONYM"
>SQL</SPAN
>-standard string functions listed in <A
HREF="functions-binarystring.html#FUNCTIONS-BINARYSTRING-SQL"
>Table 6-9</A
>.
   </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-BINARYSTRING-OTHER"
></A
><P
><B
>Table 6-10. Other Binary String Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Function</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Return Type</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Description</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Example</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Result</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>btrim</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>
        <TT
CLASS="TYPE"
>bytea</TT
> <TT
CLASS="PARAMETER"
><I
>trim</I
></TT
> <TT
CLASS="TYPE"
>bytea</TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>        Remove (trim) the longest string consisting only of characters
        in <TT
CLASS="PARAMETER"
><I
>trim</I
></TT
> from the start and end of
        <TT
CLASS="PARAMETER"
><I
>string</I
></TT
>.
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>btrim('\\000trim\\000'::bytea,'\\000'::bytea)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>trim</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="FUNCTION"
>length</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
>)</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>       Length of binary string
       <A
NAME="AEN7291"
></A
>
       <A
NAME="AEN7294"
></A
>
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>length('jo\\000se'::bytea)</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>5</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
>       <TT
CLASS="FUNCTION"
>encode</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
> <TT
CLASS="TYPE"
>bytea</TT
>,
              <TT
CLASS="PARAMETER"
><I
>type</I
></TT
> <TT
CLASS="TYPE"
>text</TT
>)
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>       Encode binary string to <SPAN
CLASS="ACRONYM"
>ASCII</SPAN
>-only representation.  Supported
       types are: base64, hex, escape.
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>encode('123\\000456'::bytea, 'escape')</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>123\000456</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
>       <TT
CLASS="FUNCTION"
>decode</TT
>(<TT
CLASS="PARAMETER"
><I
>string</I
></TT
> <TT
CLASS="TYPE"
>text</TT
>,
              <TT
CLASS="PARAMETER"
><I
>type</I
></TT
> <TT
CLASS="TYPE"
>text</TT
>)
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="TYPE"
>bytea</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>       Decode binary string from <TT
CLASS="PARAMETER"
><I
>string</I
></TT
> previously 
       encoded with <TT
CLASS="LITERAL"
>encode()</TT
>.  Parameter type is same as in <TT
CLASS="LITERAL"
>encode()</TT
>.
      </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>decode('123\\000456', 'escape')</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>123\000456</TT
></TD
></TR
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