class as a table column

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От George Young
Тема class as a table column
Дата
Msg-id 199907092055.QAA12274@ll.mit.edu
обсуждение исходный текст
Список pgsql-sql
[libpq++ with gcc egcs-2.91.66 (egcs-1.1.2 release) on RH linux 5.1
with Postgres 6.5.]
I've seen in the manual that one can create a table with a class/table
as one of the columns, e.g.:  --set (complex) attribute may be of the same type as the      --relation being defined
(ashere) or of a different complex      --type.  The type must exist in the "pg_type" catalog or be      --the one
currentlybeing defined.      --      create table newemp (name text, manager newemp)
 
and I have been able to do this in psql.
But what does this really mean?  And how does one insert or extract
data from such a column?  And what is it good for?  It seems like
maybe a powerful facility, but I really don't understand it.
Is this sort-of the same as inheriting from that class? 
Does anyone have examples of its use?
Thanks,       George
George Young,  Rm. L-204                gry@ll.mit.edu
MIT Lincoln Laboratory
244 Wood St.
Lexington, Massachusetts  02420-9108    (781) 981-2756


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