Impedance Mismatch

An impedance mismatch can occur when accessing a relational database in an object-oriented programming language. Problems can arise because object-oriented programming languages like C++ or Python have very different approaches to accessing data.

Some of these differences include:

• Type references. Object-oriented languages make heavy use of by-reference attributes, while this is typically prohibited in relational databases. Scalar types also often differ between database and OO languages.
• In OO languages, objects can be made up of other objects, while this is impossible in relational database languages for integrity.
• Relational databases have well-defined primitive operations for manipulating and querying data, while OO languages have lower-level operations.
• Relational databases have more robust approaches to transactions to preserve atomicity and consistency. The only way to guarantee this through an OO language is at the level of primitive-typed fields.

Methods to mitigate impedance mismatch include using NoSQL databases and designing relational databases with object-oriented programming languages in mind, as well as paying attention to differences between OO languages and relational databases when coding a project.