On 12/25/19 3:09 PM, stan wrote:
On Wed, Dec 25, 2019 at 02:34:43PM -0800, Adrian Klaver wrote:
On 12/25/19 12:39 PM, stan wrote:
Other approaches have been suggested, e.g. use a traditional FK
relationship. The big unknown in you present system is what:
SELECT cost_category_key from t2 where type = 'Misc'
will return. The implication is that it maybe more then one value(key) in
that case, which key would you use?
There is more that that. There is a project number, so the actuall key
represents the combination of project number, and cost category, Thire is a
constraint on T2 that assures that these combinations will be unique.
So you have the unique key for the parent record of a FK relationship.
When the 1st record for a project, that gets charged to the misc. cost
category is entered, I need to assure that combination gets inserted into
T2
When you start a new project seed it with the project number, cost
category, type='misc' record.
If not and cost_category_key: type is one to one then why have both?
Just make one unique(or PK) and the parent for the cost_category_key in t1.
--
Adrian Klaver
adrian.kla...@aklaver.com
