IBM did not spend the money it did to replace its premier database product, IMS, with another DBMS, DB2, just to enable "simple database queries". Yes, SQL was influenced by other "4th generation languages" of the era. But IBM judged -- correctly, on the evidence -- that most programmers would not take the time to master first order predicate logic or set theory.
So they came up with something that implemented the Relational Model in a simple way, one that would attract new converts. SQL has plenty of warts and defects, but its success at extinguishing every other database query language can't be denied.
So they came up with something that implemented the Relational Model in a simple way, one that would attract new converts. SQL has plenty of warts and defects, but its success at extinguishing every other database query language can't be denied.