Advice on database design / SQL for retrieving data with chronological order
- by Remnant
I am creating a database that will help keep track of which employees have been on a certain training course. I would like to get some guidance on the best way to design the database.
Specifically, each employee must attend the training course each year and my database needs to keep a history of all the dates on which they have attend the course in the past.
The end user will use the software as a planning tool to help them book future course dates for employees. When they select a given employee they will see:
(a) Last attendance date
(b) Projected future attendance date(i.e. last attendance date + 1 calendar year)
In terms of my database, any given employee may have multiple past course attendance dates:
EmpName AttandanceDate
Joe Bloggs 1st Jan 2007
Joe Bloggs 4th Jan 2008
Joe Bloggs 3rd Jan 2009
Joe Bloggs 8th Jan 2010
My question is what is the best way to set up the database to make it easy to retrieve the most recent course attendance date? In the example above, the most recent would be 8th Jan 2010.
Is there a good way to use SQL to sort by date and pick the MAX date?
My other idea was to add a column called ‘MostRecent’ and just set this to TRUE.
EmpName AttandanceDate MostRecent
Joe Bloggs 1st Jan 2007 False
Joe Bloggs 4th Jan 2008 False
Joe Bloggs 3rd Jan 2009 False
Joe Bloggs 8th Jan 2010 True
I wondered if this would simplify the SQL i.e.
SELECT Joe Bloggs WHERE MostRecent = ‘TRUE’
Also, when the user updates a given employee’s attendance record (i.e. with latest attendance date) I could use SQL to:
Search for the employee and set the
MostRecent value to FALSE
Add a new record with MostRecent set to TRUE?
Would anybody recommended either method over the other? Or do you have a completely different way of solving this problem?
