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===== Database Function Description of "concat_ignore_null" =====

=== Name ===

concat_ignore_null

=== Description ===

This function will concatenate two strings.

The concatenation operator || has been redefined to use this function.

=== Purpose ===

This function will concatenate two strings. The difference from the || operator is that our function will ignore null arguments.

=== Schema ===

<code sql>
create function concat_ignore_null(varchar, varchar) returns varchar as '
    declare
        string_1         alias for $1;
        string_2         alias for $2;
    begin
        if string_1 is null then
           return string_2;
        end if;

        if string_2 is null then
           return string_1;
        end if;

        return string_1||string_2;
     end;
' language  'plpgsql' ;

-- concat operator that ignores null arguments
create operator ||| (
  leftarg   = varchar,
  rightarg  = varchar,
  procedure = concat_ignore_null
);
</code>

=== History ===

== Used first ==

Version 2.16

== Used last ==

Still in use

== Change history ==

= Version 2.16 =

<code sql>
-- this function will concatenate two strings
-- the difference from the || operator is that our function
-- will ignore null arguments
create function concat_ignore_null(varchar, varchar) returns varchar as '
    declare
        string_1         alias for $1;
        string_2         alias for $2;
    begin
        if string_1 is null then
           return string_2;
        end if;

        if string_2 is null then
           return string_1;
        end if;

        return string_1||string_2;
     end;
' language  'plpgsql' ;

-- concat operator that ignores null arguments
create operator ||| (
  leftarg   = varchar,
  rightarg  = varchar,
  procedure = concat_ignore_null
);
</code>