Foreign key : LUSENET : MAN-EDF : One Thread

How can I make changes in the database? Do I need to download, make the changes and then upload again?

Also, how is the foreign-key number determined? Does a number have to be in that field?

Thanks- Joy

-- Anonymous, April 07, 1999


The only changes you can do are:

1) Upload new activists in batch 2) Enter manually activists at the signup page. 3) Remove activists on a one by one basis. What I call "Angry people".

Once people are uploaded, they stay uploaded. You as a manager cannot remove all of the activists. You can request us to remove them but that would be only in the case you really want to bail out for good.

The foreign key is the equivalent of their social security number, it's the identifying key that these activists might have in an outside database. It's a number. You are not required to enter this its just a field that you can use for your own purposes you can leave it blank if you want.

-- Anonymous, April 07, 1999

A foreign key is just an entry in a record that points to one and only one record in a "foreign" location (for example, a table in the same database or a listing elsewhere).

Technically, a foreign key (FK) is actually a pointer to a Primary Key (PK) in that other location. A Primary Key has a simple definition: it must be "unique and not null." This is a good reason not to use Social Security numbers as individual identifiers, by the way. Some listings you may have in a database probably won't have a SSN (i.e., won't be 'not null'), and rarely but occasionally someone will have more than one SSN (i.e., won't be 'unique').

Many other commonly used "ID numbers" are bad for this reason -- ones that are constructed from parts of names and addresses, like a lot of membership and fundraising tracking programs do. Phone numbers are terrible; not only do some people have zero, one or more phone numbers (home/office/cell/whatever), but you often find different people listed with the same phone.

One final caution on SSN: probably illegal to use in almost any application we have in the environmental movement (except for accounting purposes related to tax reporting). Some places can legally ask you for them (credit card companies and banks, for example), while many places should not but still do.


-- Anonymous, April 08, 1999

Fred is right.

I am not suggesting that anybody should use SS# as a foreign key in their databases. I use it as an example - a bad one now I see- to explain what a foreign key is.

Anyway, my only point is that a FK is a unique identifier that will be permanently afixed to an activist. We only keep a certain ammount of info on MAN's site, any more info (say voting record, membership data and so on) can be kept outside on MAN's site. This FK is what links the "in site database" to the "out of site database".

-- Anonymous, April 08, 1999

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