On 20. okt. 2013, at 04:01, Bob M <rgmatth...@orcon.net.nz> wrote: > hi > > I have a derby database and a table with over 4,000 records............…
It is easier to think about a table as a hash table or tree, rather than an array. So there isn't really a concept of first or last other than the ordering imposed by the primary key (or other index). Meaning that there isn't an builtin way to retrieve the first or oldest entry (or the newest) unless you have a column that reflects the age (could be an auto increment column). (Note that Derby is different from some other databases (e.g. Oracle) which have something called row id which would have given you this ordering column automatically) > > I wish to:- > > a) get the number of records in the table SELECT COUNT(*) FROM t > b) retrieve the last record Assuming you have a column x which imposes the order you're after: SELECT MAX(x) FROM t to get the max key SELECT * FROM t WHERE x=<max key> > c) update this record UPDATE t SET a=.., b=.. … WHERE x = <max key> > d) add a new record and INSERT INTO t VALUES(…) > e) delete the first (oldest) record DELETE FROM t WHERE x = (SELECT MIN(x) FROM t) HTH, Dyre
