The type of database in which the data are connected in different files by using common data elements or a key field is ?

Different database models organise how records in separate files relate to one another. A hierarchical database arranges records in a tree with parent and child relationships, and a network database links records through multiple owner-member pointers, both of which use structural links rather than shared data values.

A relational database instead stores data in separate tables and connects them by matching a common field, known as a key field, that appears in more than one table. For example, a student's identification number stored in one table can be matched against the same identification number in another table to bring related records together. This use of a shared key field to join independently stored files is the defining feature of the relational model.

When a question mentions files being linked through a common data element or key field rather than a fixed tree or network structure, that description points to the relational model.