The statement “this [guy] thinks the government uses SQL” demonstrates a complete and total lack of knowledge as to what SQL even is. Every government on the planet makes extensive and well documented use of it.

The initial statement I believe is down to a combination of the above and also the lack of domain knowledge around social security. The primary key on the social security table would be a composite key of both the SSN and a date of birth—duplicates are expected of just parts of the key.

If he knew the domain, he would know this isn’t an issue. If he knew the technology he would be able to see the constraint and following investigation, reach the conclusion that it’s not an issue.

The man continues to be a malignant moron

The initial statement I believe is down to a combination of the above and also the lack of domain knowledge around social security. The primary key on the social security table would be a composite key of both the SSN and a date of birth—duplicates are expected of just parts of the key.

Since SSNs are never reused, what would be the purpose of using the SSN and birth date together as part of the primary key? I guess it is the one thing that isn’t supposed to ever change (barring a clerical error) so I could see that as a good second piece of information, just not sure what it would be adding.

Note: if duplicate SSNs are accidentally issued my understanding is that they issue a new one to one of the people.

www.ssa.gov/history/hfaq.html

Q20: Are Social Security numbers reused after a person dies?

A: No. We do not reassign a Social Security number (SSN) after the number holder’s death. Even though we have issued over 453 million SSNs so far, and we assign about 5 and one-half million new numbers a year, the current numbering system will provide us with enough new numbers for several generations into the future with no changes in the numbering system.

Take this with a grain of salt as I’m not a dev, but do work on CMS reporting for a health information tech company. Depending on how the database is designed an SSN could appear in multiple tables.

In my experience reduplication happens as part of generating a report so that all relevant data related to a key and scope of the report can be gathered from the various tables.

A given SSN appearing in multiple tables actually makes sense. To someone not familiar with SQL (i.e. at about my level of understanding), I could see that being misinterpreted as having multiple SSN repeated “in the database”.

Theoretically, yeah, that’s one solution. The more reasonable thing to do would be to use the foreign key though. So, for example:

SSN Table ID | SSN | Other info

Other Table ID | SSN ID | Other info

When you want to connect them to have both sets of info, it’d be the following:

SELECT * FROM SSN_Table JOIN Other_Table ON SSN_Table.ID = Other_Table.SSN_ID