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Imagine the following tables.

Person
    - id
    - name

Place
    - id
    - name

Coverage
    - id
    - from_person_id
    - to_person_id
    - new
    - old
    - start_date
    - end_date
    - closed

CoveragePlaces
    - id
    - coverage_id
    - place_id

The rules of the application state that a "person that is covering" for another "person" will have one record in the coverage table. The coverage table contains the "from_person_id" which is a reference to the person "covering". "to_person_id" representing another "person" who is "receiving coverage". A "person" can cover for another person from a "start_date" to an "end_date" for "old" or "new" or "all" jobs and at specific "places". No single "person" can have coverage for identical places, dates, and job status (all, old or new).

As of right now, our data is stored very similar to the above. When selecting to find people currently providing coverage for another person. We would do something like this.

SELECT
    coverage.to_user_id AS user_id
FROM
    coverage
INNER JOIN
    coverage_places
        ON ( coverage.id = coverage_places.coverage_id AND coverage_places.place_id = 10 )
WHERE
    coverage.from_user_id = 150 AND
    coverage.new = 1

Although the rules of the application state that no person can have 2 records of identical coverage. The current state of the application allows for the record to be inserted, but it overrides the existing one once outputted.

We want to change this functionality and display to the user what coverage will be replaced by their existing coverage. Since their new coverage could potentially override multiple rows.

For example, if Person A is providing coverage for Person B at place1, place2, and place3 for new jobs this entire month.

Person A is also providing coverage for Person C at place1, and place2 for all (new/old) jobs the entire month.

Then Person C decides that Person D is covering for them for the entire month at place1, and place2 in place of Person A only for old patients.

Now the application needs to detect that Person A will still be covering for Person C, but only for old patients at place, and place2.

The records for the coverage explained above (before the record for persond is entered) is below.

coverage_places
    coverage_id place_id
    1 1
    1 2
    1 3
    2 1
    2 2
coverage
    id from_user_id to_user_id
    1 1 2 
    2 1 3
places
    id name
    1 place1
    2 place2
    3 place3
person
    id name
    1 persona
    2 personb
    3 personc
    4 persond

Now the application needs to display the record that it is going to replace. If the user verifies that they want to override this coverage then the application needs to modify or delete the old coverage and insert the new coverage.

Also consider if Person A decided they wanted Person E to cover for them at place1 for old jobs for the next week.

We currently have a model very similar to the above working where a lot of logic is done on the programming end to find what coverage overlaps and display not just the record that overlaps but the pieces of that record that overlap. The code has become very complex. I have decided to step back and take a look at things to see if there may be a more simple / efficient approach.

Also bear in mind that in the future the application hopes to support dynamic fields for coverage. So i can create a new field "job pay" and have another person cover for certain pay amounts.

Any ideas or suggestions would be greatly appreciated.

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1 回答 1

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由于提供的实际封面似乎是针对地点和工作类型的组合，因此我会考虑重新设计您的模型以反映这一点。我会建议这样的事情

Person
  - id
  - name

Place
  - id
  - name

Coverage
  - id
  - from_person_id
  - to_person_id
  - coverage_type
  - place_id
  - start_date
  - end_date
  - closed

然后，您将拥有每种类型/地点组合的唯一记录，并且将一个掩护替换为另一个掩护会容易得多。

这确实意味着您的应用程序可能需要做一些工作来将这些分组以用于显示目的（即，一个人正在为所有地方的所有工作覆盖另一个人）但这比在需要时尝试分解当前数据要容易得多代替一些掩护。

于 2012-04-08T09:45:26.170 回答