Databases Reference
In-Depth Information
Time Period Relationships
Along a Common Timeline
Intersects
Fills
Occupies
Aligns
Finishes
|-|
|-----------|
Figure 14.16 T
1
[finishes] P
1
.
Consider the following request for information: which
policies began on the same date as the 2009 Diabetes Wellness
Management Program ended?
The SQL written to fulfill this request is:
SELECT * FROM V_Allen_Example
WHERE pol_eff_beg_dt
ΒΌ
DATEADD(MONTH, -1,
wp_epis_end_dt)
T
1
[during] P
1
This is the relationship in which a single clock tick occurs
after the start of a period of time, and before that period of time
ends.
Figure 14.17
shows this relationship, and its place in our
taxonomy. The two dashed lines in the illustration graphically
represent T
1
and P
1
,withT
1
being the upper dashed line.
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
<
T
1
) AND (eff_end_dt
f
CTD(1)
>
T
1
)
It says that T
1
occurs during P
1
just in case P
1
starts before T
1
and ends after T
1
.
