Before databases you had only flat files or VSAM (and before that, ISAM) for your data. Good luck debugging your data in a VSAM cluster. https://en.wikipedia.org/wiki/VSAM
My apologies for not being clear. By "data structures" I meant data structures and by implication that COBOL provided an abstraction over bytes in memory or on persistent storage media. The premise of my statement is that SQL is also an abstraction over bytes in memory or on persistent storage media in similar use cases.
