Before relational databases and SQL, there was a successful industry of hierarchical databases (key-value stores), which was so utterly annihilated that not one vendor remained to give testament.
RDB has since become standard. One aspect of a "standard" is uniform interfaces or one-size-fits-all, an essential aspect of which is that it doesn't suit all needs perfectly. It's a modular approach, that involves adapting non-quite circular circles and non-quite triangular triangles to perfectly square slots. You see it in mathematics and (eg) OO polymorphism all the time. It's an unpleasant but often worthwhile tradeoff.
But at the edges, that tradeoff becomes questionable. And the web's REST is a new giant, whose clothing needs a different shape altogether. Applying RDB to it is so ill-fitting and irritating and obviously wrong that hierarchical databases have found a new home and a new life and a new name, NoSQL.
But when NoSQL attempts to spread to others, it is surprised and hurt to find them already tailored for.
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The above fable is light on detail. There are many complex issues in the NoSQL/RDB comparison, since both have adapted to the detailed problems of their respective domains. However, I think the key aspect is that RDB is meticulously thought out in terms of information, and only then adapted to specific engineering needs. Specifically, it has normal forms and schema (needed for normal forms.)
RDB has since become standard. One aspect of a "standard" is uniform interfaces or one-size-fits-all, an essential aspect of which is that it doesn't suit all needs perfectly. It's a modular approach, that involves adapting non-quite circular circles and non-quite triangular triangles to perfectly square slots. You see it in mathematics and (eg) OO polymorphism all the time. It's an unpleasant but often worthwhile tradeoff.
But at the edges, that tradeoff becomes questionable. And the web's REST is a new giant, whose clothing needs a different shape altogether. Applying RDB to it is so ill-fitting and irritating and obviously wrong that hierarchical databases have found a new home and a new life and a new name, NoSQL.
But when NoSQL attempts to spread to others, it is surprised and hurt to find them already tailored for.
---
The above fable is light on detail. There are many complex issues in the NoSQL/RDB comparison, since both have adapted to the detailed problems of their respective domains. However, I think the key aspect is that RDB is meticulously thought out in terms of information, and only then adapted to specific engineering needs. Specifically, it has normal forms and schema (needed for normal forms.)