What is a flat file database?

A flat file database refers to a single table that is organized within one data file. This structure means that all the data is stored in a single, two-dimensional array consisting of rows and columns. Each row represents a record, and each column represents a data field related to that record. This simplicity makes flat file databases straightforward to create and manage, often ideal for small datasets where relations between the data are minimal or nonexistent.

The other choices describe different types of database organizations. Multiple tables linked together by keys refer to a relational database, which is more complex and allows for relationships between different data sets. A collection of related data fields can refer to different models, not strictly a flat file setup. Lastly, a database containing complex queries implies a level of interaction and data retrieval capability that flat file databases do not inherently possess since they don't support advanced querying like relational databases do.