supergroup — compute a group's supergroup as of a given date
NUMERIC(5,3)
supergroup
(
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grp, | |
date); |
NUMERIC(5,3)
grp
;
DATE
date
;A function which returns the supergroup of a group on a given date. The GROUPS.Permanent value indicates when a group becomes permanent. Before that date a group may exist only intermittently during group fission -- as a sub-group of a larger group, the supergroup. Given a group and a date, the supergroup() function returns the ancestor group that is a real group, not a fission sub-group, on the given date.
The supergroup() function may be used to write queries that span periods of group fission and produce consistent results despite individual's having been censused in the fission sub-groups during the fission period.
The supergroup() function returns
NULL if asked to find the supergroup of
a group that has a NULL GROUPS.From_group on
a date that's before the group's Permanent date.