On 01.07.2014 at 1:23 Uhr +0100 Alex Tweedly apparently wrote:
I guess there's a meta-question about "what's a good book/source on
SQL database design ?"
I am trying to design a database. There is one table which contains,
let's say, Armed Forces Personnel
- each row is a different person
- columns include the obvious .... name, date of birth, ... that
are common to all
- there is a column saying which armed force the person is in
- and then there are additional, DIFFERENT fields depending on
which one it is
You will get lots of advice, I am sure. Database design is a science
and an art. What helps often is to identify data along the lines of
lists -- lists of values that are more or less fixed, like types of
armed forces
data -- info that is varied from data record to record, like people names
links -- tables that cross-connect data and lists (but also may have
own fields related to that connection, like a date of cross-linking)
Such division is not fixed but it helps to identify different types
of information and initial structure.
Things to consider in the next step are variations (like people
changing names), permutations (like people belonging to more than one
armed force or changing their skills), expansions (like incorporation
of addditional lists or further personal data), whether list data
need to be frozen (here I mean that renaming an entry in a list will
automatically rename it for all records; however, in some database,
the entry for a given record should remain as it was at the time of
entry even if the list is reworked later on), etc.
Next you consider various views and reports that you need to produce
and see whether the structure supports them without too many
complications.
Robert
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