Plain text, flat file, and flat-file database

I often encounter plain text, flat file, and flat-file database words, but I do not know what kind of Chinese to translate. Please kindly advise.

I have found:

(1) plain text

Refers to textual data in ASCII format. plain text is the most portable format because it is supported by nearly every application on every machine. it is quite limited, however, because it cannot contain any formatting commands.

In cryptography, plain text refers to any message that is not encrypted. Contrast with cipher text.

Plain text is also called clear text

(2) flat file

A file that has no structured interrelationship between its data records. A text document without formatting structure is considered a flat file. for example, a word processing document that has been saved as "text only" is saved without markup tags or formatting elements such as bold, italic or other font specifications and information that specifies what style to make a certain line that is used as a heading. the flat file only contains the lines of text without regard to the visual presentation of the data on the page.

(3) flat-file database

A relatively simple database system in which each database is contained in a single table. In contrast, relational database systems can use multiple tables to store information, and each table can have a different record format.

my translation is:
(1) plain text plain text
(2) flat-file unformatted file (this is the most difficult)
(3) flat-file database non-relational database