What does a database schema represent?

A database schema represents the layout of the database, which includes the definitions of tables, columns, data types, constraints, and the relationships among them. It serves as a blueprint for how the data is organized and what kind of data can be stored in each table. This structured representation is essential for ensuring data integrity and establishing how various data elements interact with one another within the database.

The schema provides a clear structure that allows users and developers to understand how to access or manipulate the data effectively. It defines not just the elements of the database but also the rules that govern the data, ensuring consistency and facilitating efficient queries.

In contrast, while unique identifiers of rows (like primary keys) are part of the schema, they do not encompass the entirety of what a schema represents. Similarly, how data is physically stored on disk relates to database storage techniques, which is distinct from the logical organization of the schema. A collection of relationships among tables could be considered part of the schema, but it does not fully capture all the aspects provided by the layout, such as the specific naming of each table and column, which is crucial for understanding the data model as a whole.