Final answer:
Advantage of relational over NoSQL databases is complex querying due to structured query language (SQL). Disadvantage is lack of schema flexibility, as relational databases require predefined schemas that are less easily altered than NoSQL's schema-less structure.
Step-by-step explanation:
When comparing relational databases to NoSQL databases, one advantage of relational databases is complex querying. This strength comes from the structured query language (SQL) that provides powerful and flexible methods to execute complex queries.
NoSQL databases, while they are typically more scalable, they do not inherently support such complex operations as easily due to their schema-less nature.
On the other hand, one disadvantage of relational databases compared to NoSQL is schema flexibility. NoSQL databases allow for easier modification of the data model without the need to predefine the schema. This can be beneficial in situations where the data structure is evolving or not well defined upfront.
Relational databases require changes to the database schema if one wishes to alter the structure of the data, which can lead to more downtime and complex data migrations.