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>Chapter 37. <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> - <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> Procedural Language</TD
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><H1
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><A
NAME="PLPGSQL-DEVELOPMENT-TIPS"
>37.2. Tips for Developing in <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
></A
></H1
><P
>    One good way to develop in
    <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> is to use the text editor of your
    choice to create your functions, and in another window, use
    <SPAN
CLASS="APPLICATION"
>psql</SPAN
> to load and test those functions.
    If you are doing it this way, it
    is a good idea to write the function using <TT
CLASS="COMMAND"
>CREATE OR
    REPLACE FUNCTION</TT
>. That way you can just reload the file to update
    the function definition.  For example:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE OR REPLACE FUNCTION testfunc(integer) RETURNS integer AS '
          ....
end;
' LANGUAGE plpgsql;</PRE
><P>
   </P
><P
>    While running <SPAN
CLASS="APPLICATION"
>psql</SPAN
>, you can load or reload such
    a function definition file with
</P><PRE
CLASS="PROGRAMLISTING"
>\i filename.sql</PRE
><P>
    and then immediately issue SQL commands to test the function.
   </P
><P
>    Another good way to develop in <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> is using a
    GUI database access tool that facilitates development in a
    procedural language. One example of such as a tool is
    <SPAN
CLASS="APPLICATION"
>PgAccess</SPAN
>, although others exist. These tools often
    provide convenient features such as escaping single quotes and
    making it easier to recreate and debug functions.
   </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="PLPGSQL-QUOTE-TIPS"
>37.2.1. Handling of Quotation Marks</A
></H2
><P
>   Since the code of a <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> function is specified in
   <TT
CLASS="COMMAND"
>CREATE FUNCTION</TT
> as a string literal, single
   quotes inside the function body must be escaped by doubling them.
   This can lead to
   rather complicated code at times, especially if you are writing a
   function that generates other functions, as in the example in <A
HREF="plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN"
>Section 37.6.4</A
>.  This chart may be useful
   as a summary of the needed numbers of quotation marks in
   various situations.
  </P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>1 quotation mark</DT
><DD
><P
>      To begin and end the function body, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FUNCTION foo() RETURNS integer AS '...'
    LANGUAGE plpgsql;</PRE
><P>
      Anywhere within the function body, quotation marks <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>must</I
></SPAN
>
      appear in pairs.
     </P
></DD
><DT
>2 quotation marks</DT
><DD
><P
>      For string literals inside the function body, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>a_output := ''Blah'';
SELECT * FROM users WHERE f_name=''foobar'';</PRE
><P>
      The second line is seen by <SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> as
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT * FROM users WHERE f_name='foobar';</PRE
><P>
     </P
></DD
><DT
>4 quotation marks</DT
><DD
><P
>      When you need a single quotation mark in a string constant inside the function
      body, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>a_output := a_output || '' AND name LIKE ''''foobar'''' AND xyz''</PRE
><P>
      The value actually appended to <TT
CLASS="LITERAL"
>a_output</TT
> would be:
      <TT
CLASS="LITERAL"
> AND name LIKE 'foobar' AND xyz</TT
>.
     </P
></DD
><DT
>6 quotation marks</DT
><DD
><P
>      When a single quotation mark in a string inside the function body is
      adjacent to the end of that string constant, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>a_output := a_output || '' AND name LIKE ''''foobar''''''</PRE
><P>
      The value appended to <TT
CLASS="LITERAL"
>a_output</TT
> would then be:
      <TT
CLASS="LITERAL"
> AND name LIKE 'foobar'</TT
>.
     </P
></DD
><DT
>10 quotation marks</DT
><DD
><P
>      When you want two single quotation marks in a string constant (which
      accounts for 8 quotation marks) and this is adjacent to the end of that
      string constant (2 more).  You will probably only need that if
      you are writing a function that generates other functions.  For
      example:
</P><PRE
CLASS="PROGRAMLISTING"
>a_output := a_output || '' if v_'' || 
    referrer_keys.kind || '' like '''''''''' 
    || referrer_keys.key_string || '''''''''' 
    then return ''''''  || referrer_keys.referrer_type 
    || ''''''; end if;''; </PRE
><P>
      The value of <TT
CLASS="LITERAL"
>a_output</TT
> would then be:
</P><PRE
CLASS="PROGRAMLISTING"
>if v_... like ''...'' then return ''...''; end if;</PRE
><P>
     </P
></DD
></DL
></DIV
><P
>    A different approach is to escape quotation marks in the function body
    with a backslash rather than by doubling them.  With this method
    you'll find yourself writing things like <TT
CLASS="LITERAL"
>\'\'</TT
> instead
    of <TT
CLASS="LITERAL"
>''''</TT
>.  Some find this easier to keep track of, some
    do not.
   </P
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