Are there schemaless relational databases?

Question

Database

Are there relational databases for which it is not necessary to set and design a schema in advance?

Answer 1

A relational database is a database based on the relational data model .

Relational data model (RMD) is a logical data model, an applied theory of database construction, which is an application to data processing problems of such sections of mathematics as set theory and first-order logic.

Relationship is a fundamental concept of the relational data model . For this reason, the model is called relational (from the English relation - “relationship”).

Let a set of data types T1, T2, ..., Tn, also called domains, be given, not necessarily different. Then an n-ary relation R, or a relation R of degree n, is a subset of the Cartesian product of the sets T1, T2, …, Tn.
The relation R consists of a header (schema) and a body. The header is a set of attributes (named occurrences of the domain in the relation header), and the body is a set of tuples corresponding to the header.

In general, it’s bad manners to answer the question with quotes from the wiki, but damn it, these Russian Wikipedia articles are good, there’s nothing to even add.
Will you draw your own conclusions? Let me help you: a schemaless relational base is a car that has had its wheels, engine, and body removed. Is it still a car or not?

Answer 2

schemaless relational

- mutually exclusive characteristics:

A relational database is a digital database based on the relational model ... This model organizes data into one or more tables (or "relations") of columns and rows, with a unique key identifying each row

for which it is not necessary to set and design a scheme in advance

How will your data be stored? Like in a garbage can? Even NoSQL databases require some schematization.
There are technologies that allow you not to write SQL queries yourself, incl. to create tables, - ORM.

Answer 3

https://neo4j.com/
Didn't they mean this by chance?) Graph DB, you don't need to set schemas, relationships can be built

Answer 4

In theory, most NoSQL databases are schemaless, each record has the right to have its own structure within certain limits

Answer 5

memcache

Answer 6

Probably the dBase variant will partially fall under such criteria - such as flat tables implying a relation - that is, links between tables, but in fact a set of dbf-files (tables) that can exist without a schema in the form of "loose")
In general, a schema is a relationship aka relation and therefore a relational database in any case implies a scheme, but you can keep them virtually in your head, and not use database mechanisms for this - we get a relational database without relations)
Naturally, the latter is akin to cheating a taxi driver - paying for a trip, but not going)