It is generally used for stand-alone lists. When files must be related (customers to orders, vendors to purchases, etc.), a relational database manager is used, not a flat file manager.

SQL statements are used both for interactive queries for information from a relational database and for gathering data for reports. There are a number of database categories, from basic flat files ...

Flat file and relational databases The simplest databases store data in a single file, where each record is identified as a new line and each row can be separated by a comma.

In non-relational "hierarchical" and "network" databases, records in one file contain embedded pointers to the locations of records in another, such as customers to orders and vendors to purchases.