Databases Reference
In-Depth Information
Dec10
DELETE FROM Policy [P861]
Jan10
1
May10
Aug10
2
1
2
1
3
4
3
5
2
1
4
3
6
5
Dec10
Jan
2010
Row
#
1
Jan
2011
Jan
2012
Jan
2013
Jan
2014
oid
eff-beg
eff-end
epis-
beg
type
asr-beg
asr-end
client
copay
row-crt
P861
P861
P861
P861
P861
P861
9999
Jan10
May10
Jan10
$15
$15
$20
$20
$20
$20
Jan10
Jan10
C882
HMO
HMO
HMO
HMO
PPO
PPO
2
3
4
5
6
May10
May10
9999
Jan10
Jan10
Jan10
Jan10
Jan10
C882
May10
May10
Jan10
May10
Aug10
9999
May10
C882
May10
Aug10
Aug10
Aug10
9999
Aug10
Aug10
C882
9999
Dec10
Aug10
Dec10
C882
Aug10
Dec10
9999
C882
Dec10
Figure 7.17 Basic Scenario, Temporal Delete: After the Second Physical Transaction.
(iv) In December 2010, we terminate this episode, effective on
that same date. The episode still has three versions, but
is now a closed episode. From this point in time, until
further notice, what we assert about this episode of P861
is rows 2, 4 and 6.
While updates and deletes are very different actions as
applied to a non-temporal table, temporal updates and temporal
deletes actually result in very similar actions applied to an
asserted version table. As we have seen, the first two physical
transactions for a temporal update withdraw the current asser-
tion, and replace it with a new currently asserted version which
occupies all the effective time of the withdrawn assertion other
than the effective time the superceding version will occupy. In
most cases, including this basic scenario, that means that the
replacement version will have the same effective begin date as
the withdrawn version, and will have the current date as its
effective end date. The superceding version picks it up from
there. A temporal delete is simply a temporal update for which
there is no superceding version, but instead only, if necessary,
one or two (but never more than two) replacement versions.
We conclude by pointing out a subtlety of the graphic nota-
tion used here. In
Figure 7.17
, note that the “above the calendar
timeline” graphics for row 1, 3 and 5 extend
through
December
2010, while the graphic for row 6 extends
up to
December
