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which came first, SQL or relational databases?
If Treasury uses COBOL, then their systems think the year is 1925
Yes, System R (another IBM product) was widely considered to be first commercial relational db. This was late 60s I think.....sometime in the 70s that "migrated" into what we know as SQL.
Interestingly, really "SQL" is just the query language....so what we call "SQL DB" is a relational database with a "SQL Syntax" interface.
I guess SSN is not a primary key
Even if its not a primary key, it could still have UNIQUE constraint applied.
I imagine there a valid reasons why they don't have it set. The amount of people either unintentionally or intentionally using the wrong SSN is probably non-trivial. Having it as a unique/primary key would prohibit you from doing some other transaction involving that person.....
I mean technically a SSN is "only" supposed to refer to your social security account, it was never intended to become a universal identifier....
I can't wait for the next judical activist to rule on primary keys, foreign keys, unique constraints, inner/outer joins.
No master/slave architecture! 13th amendment prohibits any kind of slave.
Is there a good reason for using the wrong SSN?
It was accessible via SQL dialect from within COBOL programs but was originally all part of the "system"
I see this at work sometimes. On IBMs zOS it is possible to read data from the database without going through DB2 SQL itself. This is also the reason why DB2 handles shemas and users in a quirky way.
Its a complicated question to answer because we don't have enough data. A few points: