What is a Flat File, or Flat File Database?

8 min read

Updated: May 1, 2023

Chances are, you’ve worked on or with a flat file in your day-to-day life or work without even realizing it. The simplest definition of a flat file is a plain text file, with no relational information to other files or database information. This can be a plain text file, a tabular format such as CSV, TSV, or Excel spreadsheet, or a binary file. A flat file database is a database consisting of a single such table, which can be as large or small as necessary. Technically speaking, a simple list of names, addresses, and phone numbers on a sheet of paper can be considered a flat file database. 

Flat file databases are likely some of the first computer files ever created, as it can be assumed that the punch card files created by Herman Hollerith for the US Census Bureau in the 1890s did not have cards indexing other cards, or otherwise relating individual records to one another. CSV files and other flat file formats have been in steady use in the decades since, seeing fairly little change over the years because the simple nature of the files ensured both continued usefulness, as well as usability. The simple structure means they take up little space and can be easier for programmers to reference.

What is a Flat File used for?

Flat files are often used for importing and exporting data because they are a simple and flexible way to transfer data between different software applications or systems. Flat files are typically stored in plain text format, with each line representing a single record, and each record consisting of a set of fields separated by a delimiter such as a comma or a tab.

This format is widely supported by many software applications and can be easily read and processed by a variety of programming languages and tools. Moreover, flat files do not require any special software or database management systems to work with, making them a convenient and lightweight option for data transfer tasks.

Flat files are also easy to create and edit using a simple text editor, which means that users can quickly generate new files or modify existing ones as needed. This makes it possible to customize the structure and content of flat files to meet specific import or export requirements, such as selecting specific fields or records to include or exclude, or formatting the data in a particular way.

Flat File vs Relational Databases

The key difference between flat file and relational databases is that a flat file does not contain any relational data. The records within the flat file database do not point to, depend on, or reference any other files within the database. This makes a flat file simpler to create, maintain, and in some cases call upon programmatically. However, it also means there can be a great deal of redundancy, and the data is more prone to error. On the other hand, a relational database consists of entities, attributes, and relationships. If an attribute or relationship changes, it is changed across the database. This ensures data integrity and consistency but is much more difficult and time-consuming to set up and maintain. 

Why Flat Files endure

Flat files are used for a number of reasons and in a number of ways in the modern world. It can be as simple as a large customer list used to interact with a company website. It could be a simple company directory. One of the key reasons for their longevity and popularity is their portability – because of their simplicity, they can often be read/translated directly by other systems with minimal effort. 

Flat files are simple to create as well. They consist of files, columns, fields, records, and characters, and as a result, are often easier to maintain and create than more complicated relational file systems. Many are human-readable and easy to create even without extensive knowledge of programming or computers (binary files can be flat as well, this would be a possible exception).

For example, let’s look at a simple table that could come from any spreadsheet.

First Name Last Name  Street Address       CityZip Code  Phone number
BrianWilson1234 Steven St.San Diego91911555-444-1132
JimmyPage3311 Zeppelin DriveLos Angeles  90210321-123-1234
LitaFord3232 Robinson AveDetroit48206234-234-2324
Nancy Wilson4545 Heart St.Seattle98111345-678-9090

If you were asked to fill in the last line, you would have no issues extrapolating how and in what order to fill in the information, provided you knew the information to be added.

The simpler the file, the simpler it is to run a query against it. Columns in a flat file are restricted to specific data types. Each line forms a record. Delimiters ensure the data format is limited to a fixed maximum width or a specific number of characters. They also help to make it easier to find different fields within a record. This makes it very easy for an application to call on specific data within the file. 

Limitations of Flat Files

One of the key limitations of flat files is the potential for duplication of data. There can be numerous entries for a single individual in a list of transactions for example. In a flat file, these entries are not correlated with one another, and cannot be, except by queries run against the file by another application. Along with this duplication is the potential for error. While it is easy to enter data into a spreadsheet or CSV file in a predictable manner, it is also equally easy for human error to creep in. In a spreadsheet with thousands of records, a misspelled name or improperly configured email address can be difficult to spot. This is one of the reasons that Flatirons Fuse covered the importance of validation for CSV data imports in previous blogs.

In addition, there is no relational integrity. For example, if there are multiple entries for a particular person in a flat file, for example, numerous transactions for a Charlie Brown, and his address or phone number changes, the data must be changed manually for each entry in the file. 

Flat Files in Use Today

Linear stores of NoSQL data, JSON formatted data, and basic spreadsheets can all be considered modern implementations of flat file databases seen in common use. Indeed, our most commonly used operating systems (Windows, Apple, Linux, etc.) make use of a series of flat file databases.

One of the most common flat file formats in use today is the CSV file format we’ve covered well in the past. These files, along with similar formats such as semi-colon delimited and .TSV (tab-separated value), is used to transfer data between disparate systems via import/export. Many of the most common databases today offer an option to import or export to CSV (Oracle, SQL, Cassandra, and many others). 


The simplicity and transferable nature of flat files ensure that they will not be going away any time soon. Spreadsheets are a staple of the business world, and CSVs used to import data to other databases, websites, and applications. While there are challenges with the reliability and integrity of flat file formats, they can be handled efficiently and cleanly with the right tools. For importing data between systems, consider a white-label, custom-configured CSV importer such as Flatirons Fuse, which is an alternative to Flatfile and an alternative to CSVBox.

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