Why does LINQ sometimes generate inefficient SQL queries?

Inefficient SQL is generated when LINQ expressions are not translatable or poorly structured.

LINQ providers translate queries literally. Complex projections, nested methods, or client-side functions may force suboptimal SQL such as multiple subqueries or unnecessary joins. Lack of proper indexing or improper navigation property usage can further degrade query plans. EF Core cannot always optimize logic like a human DBA, so query structure matters significantly.