Databases Reference
In-Depth Information
Time Period Relationships
Along a Common Timeline
Intersects
Fills
Occupies
During
|-|
|------------|
Figure 14.17 T
1
[during] P
1
.
Consider the following request for information: which
policies began before the 2009 Diabetes Wellness Management
Program started, and ended after it started?
The SQL written to fulfill this request is:
SELECT * FROM V_Allen_Example
WHERE pol_eff_beg_dt
<
wp_eff_beg_dt
AND DATEADD(MONTH,
1, pol_epis_end_dt)
>
wp_eff_beg_dt
T
1
[occupies] P
1
This not an Allen relationship. It is the node in our taxonomy
of Allen relationships which, when one of the time periods is a
point in time, includes the [starts], [finishes], and [during]
relationships. In other words, it combines the [during]
relationships with the [aligns] relationships. These are all the
relationships in which a time period (of more than one clock
tick) includes a point in time.
The predicate for this relationship, as it holds between a
period of time expressed as a pair of dates using the closed-open
convention, and a point in time, is:
(eff_beg_dt
<ΒΌ
T
1
) AND (eff_end_dt
>
T
1
)
