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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 BLOB with SUB_TYPE TEXT for all cases
except list of BLOB with different subtype.
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