Comment on How does this pic show that Elon Musk doesnt know SQL?
DahGangalang@infosec.pub 1 week agoBut they are implying SSN to SSN+Birthdate is a one-to-many relationship. Since SSN to SSN should be one-to-one, you can conclude the SSN to Birthdate is one-to-many, right?
natecox@programming.dev 1 week ago
No, who said there was a relationship?
A compound key is a composite key where one or both sides can be foreign keys to other tables themselves; it’s a safe assumption this is probably true in a large data set like social security. A composite key is a candidate key (a uniquely identified key) made up of more than one column.
This basically means that there is a finite number of available SSNs because they’re only 10 digits long and someone intends to recycle SSNs after the current user of one dies. Linking it to birthday is “unique enough” as to never recur.
DahGangalang@infosec.pub 1 week ago
I think I was getting some wires crossed and/or misunderstood what geoff (parent commentor to my last comment) was saying, so my comment may be misdirected some.
But according to The Social Security FAQ page, SSNs are not recycled, so that data (especially when compounded and hashed with other data) should be able to establish a one-to-one relationship between each primary key and an SSN, thusly having SSNs appear associated with multiple primary keys is a concern.
Other comments have pointed to other explanations for why SSNs could appear to occur multiple times, but those amount to “it appeared in a different field associated with the same primary key”. I think thats the most likely explanation of things.
jj4211@lemmy.world 1 week ago
Note that it being only part of a key is a technology choice that does not require the reality map to it. It may seem like overkill, but someone may not trust the political process to preserve that promise and so they add the birthdate, just in case something goes sideway in the future. Los of technical choices are made anticipating likely changes and problems and designing things to be extra robust in the face of those
natecox@programming.dev 1 week ago
Yeah this strikes me as safeguarding against a possible bad decision.