[reaanb2]

In my view, the O/R impedance mismatch derives from a number of shortcomings. Many developers view entities as containers of their attributes and involved only in binary relationships, rather than the subjects of n-ary facts. They map directly from a conceptual model to a physical model, bypassing logical modeling. They view OOP as a data modeling system, and reinvent network data model databases and navigational code on top of SQL.

[mcphage]

In that case, the mismatch is between "What developers need" and "What SQL provides".

[CRConrad]

Or maybe between "What developers want / think they need" and "What SQL provides".