Databases

A table within a database. The relational database now consists of four entities each containing data. The patient entity stores information about the animal, the owner entity stores the information about the owner of the animal or animals, and vet information is stored in the vet entity. The final entity is the treatment entity, which stores information about the treatment each patient received as well as the date of the treatment.

An issue that can occur because of incorrect handling in a database

An RDBMS is a sophisticated software application (such as MySQL, PostgreSQL, or Oracle) that enables users to create, update, and administer a relational database. It organizes data into structured tables (relations) and uses SQL as the standard language for interaction. Unlike a simple database, an RDBMS ensures Referential Integrity and provides tools for data security, concurrent user access, and complex querying.

You cannot add details for a vet without adding information about a patient and an owner, meaning that a vet has to treat a patient before being added to the database.

You cannot delete data without all data in the record being deleted. For example, if you delete all the information about a vet then you lose all the information about the parent and owner.

If an update is needed (such as a change of address) and you do not change all records, then you will have different data in the database and no longer know which is the correct version.

A flat-file database is a simple, single-table database stored as a plain text file (e.g., CSV, TSV, or JSON) where each row represents one record. Lacking complex relationships (non-relational) and indexes Data is stored in a single entity.

Primary keys are unique identifiers for an instance in an entity. (no two records can have the same PK)

Foreign Key: An attribute that creates a relationship between the instances by pointing to a Primary Key in another table

Sometimes there are no unique values in a record, so you have to link different values together to make them unique. This can be seen in the treatment entity.

Sometimes, when there are no unique values in a record, data from the attributes can be placed together to create a unique key.

Cardinality is the type of relationship between the entities. - 1to 1 etc

• Community support: There are multiple streams of support for users of relational databases. • Concurrency control: Relational databases can be used by concurrent users without error using ACID properties (this will be explained further in this topic). • Data consistency: Due to the lack of data repetition, data is more consistent. Data integrity: Due to the lack of data repetition, data is more likely to be correct. • Data retrieval: Using SQL commands, data retrieval is easier. • Reduced data duplication: Due to the use of entities and relationship, there is • less data duplication. • Reduced redundancy: As data is stored across entities using relationship links, • there is less redundant data. • Reliable transaction processing: Relational databases have several checks that • occur when transactions take place to ensure that the transactions are reliable. • Scalability: Relational databases are easier to scale than flat file databases. • Security: Relational databases have built-in security to support a multiuser • environment.

Big data scalability: Relational database models are not the best model for storing data that will be mined to make complex decisions. Design complexity: The different entities and models within the database can be complex and challenging to implement. Hierarchical data handling: The nature of the database model means trees are stored in a hierarchical manner. This can lead to inefficient traversal of the tree, especially if there are deep hierarchical layers. Rigid schema: The schemas of the database are rigid data types, and relationships must conform to very specific rules. \dentify suitable cardinality and modality relationships for: e teacher and student * class and teacher e 700and animal « person and clothes * animals and children. Object-relational impedance mismatch: Relational databases are useful for storing data in dedicated databases. However, if the data then needs to be used in an object-oriented space, for example, when dealing with big data, sometimes the models might not be fully compatible. Unstructured data handling: Unstructured data that does not follow the rigid scheme of the database model can be difficult to place within the model.

A database schema is a blueprint of the database that identifies the different | Conceptual model | entities (tables), attributes (fields) and relationships (links) within the database,