Types of Databases [backup]

A database is an organized collection of data that can be managed and accessed easily. Primarily, databases are divided into two types; Relational and Non-RelationalNon-relational databases are also called NoSQL databases, stands for Not-Only SQL. databases.

Relational databases

Relational databases adhere to particular schemas before storing the data. The data stored in relational databases has prior structure. Mostly, this model organizes data into one or more relations (also called tables), with a unique key for each tuple (instance). Each entity of the data consists of instances and attributes where instances are stored in rows and the attributes of each instance are stored in columns. Since each tuple has a unique key, therefore, a tuple in one table can be linked to a tuple in other tables by storing the primary keys in other tables generally known as foreign keys.

A Structure Query Language (SQL) is used for manipulating the database; insertion, deletion, and retrieval of data.

There are various reasons for the popularity and dominance of relational databases which include simplicity, robustness, flexibility, performance, scalabilityTraditional databases are vertically scalable. Vertical scaling has limits. One might reach a point when more compute, memory, storage, or networking capability could not be added to a single node., and compatibility in managing generic data. Relational databases provide the Atomicity, Consistency, Isolation, and Durability (ACID) properties to maintain the integrity of the database. ACID is a powerful abstraction that simplifies complex interactions with the data and hides many anomalies (like dirty reads, dirty writes, read skew, lost updates, write skew, phantom reads) behind a simple transaction abort.

But ACID is like a big hammer (by design so that it is generic enough for all the problems), and if some specific application only needs to deal with a few anomalies, there is a window of opportunity to use a custom solution for higher performance (but added complexity).

Let’s discuss ACID in detail:

• Atomicity: A transaction is considered an atomic unit. Hence, all the statements within a transaction will successfully execute, or none of them will execute. If a statement fails within a transaction; it should be aborted and rollback.

• Consistency: At any given time the database should be in a consistent state, and it should remain in a consistent state after every transaction. For example, if multiple users want to view a record from the database it should return a similar result each time.

• Isolation: In the case of multiple transactions running concurrently, they should not be affected by each other. The final state of the database should be the same as the transactions were executed sequentially.

• Durability: The system should guarantee that completed transactions will survive permanently in the database even in system failure events.

There are various database management systems (DBMS) used to define relational database schema along with other operations such as to store, retrieve, and run SQL queries on data. Some of ...