A database organizes data through entities, attributes and relationships. - **Entities** are the abstract representations of the objects of interest (analogous to a [[Class]] in programming). - **Attributes** are the characteristics of interest for which data are stored. - **Relationships** are associations between two or more entities. These are named with a verb by convention. These three are often described using an [[entity-relationship diagram]]. Each individual record is referred to as an **instance**. Each instance will have an **identifier**, which is a special attribute used to identify a specific instance. Databases include user data, metadata, application data, and indices. - **User data** refers to the data users work with, often stored in tables. - **Metadata** are data about data. These describe the data including table name, column name, data type, primary keys, etc. Metadata are stored in system tables accessible only to administrators. - **Indices** store representations of data to facilitate storing, searching and sorting. - **Application metadata** include forms, reports and queries. [[base/transaction]] [[database backup]] [[CAP]] [[google sheets]] [[database management system]] [[knowledge discovery in databases]] [[from data to insight]] [[relational database]] [[Postgres]] [[SQL]] [[database normalization]] [[database markup language]] [[schema]] [[entity-relationship diagram]] [[data warehouse]] [[Snowflake]] [[vector database]] [[Chroma]] [[project organization for databases]] [[ACID]] https://core0.staticworld.net/assets/media-resource/16281/infoworld_which_database_deep_dive.pdf