Database
A repository to store data. For example, a database might store all of the data associated with finance in a large company, information about your CD and DVD collection, or the records of an online store.
Table
A part of a database that stores data related to an object, thing, or activity. For example, a table might store data about customers. A table has columns, fields, or attributes. The data is stored as rows or records.
Attributes
The columns in a table. All rows in a table have the same attributes. For example, a customer table might have the attributes name, address, and city. Each attribute has a data type such as string, integer, or date.
Rows
The data entries stored in a table. Rows contain values for each attribute. For example, a row in a customer table might contain the values “Matthew Richardson,” “Punt Road,” and “Richmond.” Rows are also known as records.
Relational model
A formal model that uses database, tables, and attributes to store data and manages the relationship between tables.
(Relational) database management system (DBMS)
A software application that manages data in a database and is based on the relational model. Also known as a database server.
SQL
A standard query language that interacts with a database server. SQL is a set of statements to manage databases, tables, and data. Despite popular belief, SQL does not stand for Structured Query Language and isn’t pronounced Sequel: it’s pronounced as the three-letter acronym S-Q-L and it doesn’t stand for anything.
Constraints
Restrictions or limitations on tables and attributes. A database typically has many constraints: for example, a wine can be produced only by one winery, an order can’t exist if it isn’t associated with a customer, and having a name attribute is mandatory for a customer.
Primary key
One or more attributes that contain values that uniquely identify each row. For example, a customer table might have the primary key named cust ID. The cust ID attribute is then assigned a unique value for each customer. A primary key is a constraint of most tables.
Index
A data structure used for fast access to rows in a table. An index is usually built for the primary key of each table and can then be used to quickly find a particular row. Indexes are also defined and built for other attributes when those attributes are frequently used in queries.
Entity-relationship (ER) modeling
A technique used to describe the real-world data in terms of entities, attributes, and relationships.
Normalized database
A correctly designed database that is created from an ER model. There are different types or levels of normalization, and a third-normal form database is generally regarded as being an acceptably designed relational database.
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