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NoSQL (originally referring to "non- SQL " or "non-relational") [ 1 ] is an approach to database design that focuses on providing a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Instead of the typical tabular structure of a relational database, NoSQL databases ...
In database systems, consistency (or correctness) refers to the requirement that any given database transaction must change affected data only in allowed ways. Any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof. This does not guarantee correctness ...
A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. The constraint must be a predicate. It can refer to a single column, or multiple columns of the table. The result of the predicate can be either TRUE, FALSE, or UNKNOWN, depending on the presence of NULLs.
The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. [citation needed] These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the ...
Definition: Referential integrity is a database concept that ensures that relationships between tables remain consistent. When one table has a foreign key to another table, the concept of referential integrity states that you may not add a record to the table that contains the foreign key unless there is a corresponding record in the linked table.
Loose coupling. In computing and systems design, a loosely coupled system is one. in which components are weakly associated (have breakable relationships) with each other, and thus changes in one component least affect existence or performance of another component. in which each of its components has, or makes use of, little or no knowledge of ...
Functional dependency. In relational database theory, a functional dependency is the following constraint between two attribute sets in a relation: Given a relation R and attribute sets , X is said to functionally determine Y (written X → Y) if each X value is associated with precisely one Y value. R is then said to satisfy the functional ...
Isolation (database systems) In database systems, isolation is one of the ACID (Atomicity, Consistency, Isolation, Durability) transaction properties. It determines how transaction integrity is visible to other users and systems. A lower isolation level increases the ability of many users to access the same data at the same time, but also ...