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Posted by --CELKO-- on 02/24/07 04:57
>> When I use a single table I use constraints to enforce my business logic, but what do I do when I normalize a single table into multip can easilyle tables. <<
The same thing -- use constraints to enforce business logic.
>> For example, imagine that my initial table has the columns ID, Name, Salary with the constraint that Salary is not NULL. <<
Your data element names are all wrong. There is no such magical
creature as a Universal ID; this is OO or file system record numbers.
Name of what? Employee, maybe? Salary_type? Salary_amt? In fact, we
have no ideas what the name of this table is!!
>>Now imagine that I break this into two tables, one with ID and Name and another with ID and Salary. <<
We fire you for not having taken a data modeling course and knowing
about attribute splitting. The rule is that all the attributes of an
entity stay in one and only one table. Can I assume that this is
Personnel (emp_id, emp_name, salary_amt) and that the three are
required attributes?
>> I would like to have a constraint that prevents the creation of a row with (ID,Name) in the first table unless a corresponding row in the second table is also created. <<
You do not need that if you keep your **already normalized** table.
I am guessing that you are really trying to ask about DRI actions, but
don't have enough background to know the concepts of normalization and
how they work together.
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