SQL Language Extension: LIST

Function:
    This function returns a string result with the concatenated non-NULL
    values from a group. It returns NULL if there are no non-NULL values.

Authors:
    Oleg Loa <loa@mail.ru>
    Dmitry Yemanov <dimitr@firebird.org>

Format:

  <list function> ::=
      LIST '(' [ {ALL | DISTINCT} ] <value expression> [',' <delimiter value> ] ')'

  <delimiter value> ::=
      { <string literal> | <parameter> | <variable> }

Syntax Rules:
    1) If neither ALL nor DISTINCT is specified, ALL is implied.
    2) If <delimiter value> is omitted, a comma is used to separate
       the concatenated values.

Notes:
    1) Numeric and datetime values are implicitly converted to strings
       during evaluation.
    2) The result value is of type VARCHAR(32765), so the LIST function
       should be used carefully, as Firebird limits the maximum
       result set width by 64KB.
    3) Ordering of values within a group is implementation-defined.

Examples:

A)
  SELECT LIST(ID, ':')
  FROM MY_TABLE

B)
  SELECT TAG_TYPE, LIST(TAG_VALUE)
  FROM TAGS
  GROUP BY TAG_TYPE