I'm trying to understand Keys, I do for the most part, but in reading the well recommended book 'Database Design for Mere Mortals' I got a bit confused.
A check for worthy primary key designation is to ask what fields are "indirectly" identified by the PK, then the book says to slash such a field --I suppose later to put it into a separate or subset table; however, turning the page, the field is there and never removed from the final version of the book's example table.
(If you have this book it is Chap. 8, pgs. 224-226.)
Next, again from reading this book, I am told that when i create Primary Keys manually (or artificially, i.e., not naturally occurring fields) e.g., making a field called 'table1.people_id' as my Primary Key (auto-incrementing), and in another table the Primary Key 'table2.location_id' (auto-incrementing), the book leads me to believe that each of these *two table's Primary Key's field values cannot be the same*.
that is, that if the values for the field 'table1.people_id' rows is "1" - "50", then the field values for 'table2.location_id' (or any other table) cannot also be "1" - "50".
Huh??? Is that long winded stuff I just wrote simply wrong? (I think it is, but need clarity.) *If it is correct, then how is such a thing accomplished?
Thanks.
Ted
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