Navigating the myriad of data types in PostgreSQL can sometimes feel like deciphering an ancient text, especially when seemingly distinct options behave identically. A common point of confusion for developers and database administrators alike arises when comparing CHARACTER VARYING and VARCHAR in PostgreSQL. While the SQL standard defines them with subtle nuances, PostgreSQL’s implementation streamlines this, leading to practical implications that are crucial for efficient database design and performance. Understanding the core distinctions, or lack thereof, within PostgreSQL’s ecosystem is essential for making informed decisions about how you store and manage textual data. This article aims to demystify these two widely used string data types, exploring their origins, their behavior in PostgreSQL, and offering practical guidance for your database schemas.

Understanding VARCHAR in PostgreSQL

The VARCHAR(n) data type is a staple in relational databases, designed to store character strings of varying lengths, up to a specified maximum of ’n’ characters. When you declare a column as VARCHAR(50), for instance, PostgreSQL allows you to store strings ranging from zero characters up to fifty characters. Any string shorter than the specified ’n’ will consume only the necessary storage space plus a small overhead, making it highly efficient for managing text fields where the length can vary significantly.

This variable-length characteristic is a key advantage over fixed-length character types like CHAR(n), which always consume ’n’ bytes, padding shorter strings with spaces. For instance, storing “hello” in a CHAR(50) column would still use 50 bytes (45 of which would be spaces), whereas in VARCHAR(50), it would only use 5 bytes plus overhead. This efficiency is critical for optimizing disk space and I/O operations, especially in large databases with numerous text fields.

In PostgreSQL, if you declare a column simply as VARCHAR without specifying a length, it functions identically to the TEXT data type, allowing strings of any length up to the system’s limits. This flexibility makes VARCHAR a go-to choice for a wide range of applications, from storing names and addresses to product descriptions and comments, where the exact length of the data isn’t always predictable but a maximum constraint is desired for data integrity or application logic.

Delving into CHARACTER VARYING

CHARACTER VARYING(n) is another data type specified by the SQL standard for storing variable-length character strings, again with an optional maximum length ’n’. From a purely semantic standpoint as defined by the SQL standard, it is conceptually identical to VARCHAR(n). Both are designed to handle strings where the length can differ from row to row, ensuring that only the required storage is consumed for the actual data.

Historically, different database systems might have had subtle internal distinctions or preferred one syntax over the other. However, in modern PostgreSQL, this distinction is largely academic. When you declare a column using CHARACTER VARYING(n), PostgreSQL internally treats it precisely the same way it would treat a VARCHAR(n) column. There are no differences in storage mechanism, performance characteristics, or the functions that can be applied to these columns.

This synonymity is a design choice by the PostgreSQL development team to simplify the user experience and ensure broad compliance with the SQL standard without introducing unnecessary complexity or performance variations. Therefore, whether you choose to use CHARACTER VARYING or VARCHAR in your PostgreSQL schema definitions, the underlying behavior and efficiency will be identical.

The PostgreSQL Perspective: Are They Truly Different?

The short and definitive answer to whether CHARACTER VARYING and VARCHAR are different in PostgreSQL is: no, they are not. In PostgreSQL, these two data type declarations are completely synonymous. This means that if you define a column as VARCHAR(100) and another as CHARACTER VARYING(100), they will behave identically in every conceivable way—storage, performance, indexing, and available functions. This implementation choice aligns with the PostgreSQL project’s philosophy of offering robust SQL standard compliance while prioritizing usability and avoiding redundant functionalities that could confuse users or introduce subtle, unexpected behaviors across different syntaxes.

This synonymity is explicitly stated in the PostgreSQL documentation, which serves as the ultimate authority on its behavior. According to the official PostgreSQL documentation on Character Types, both VARCHAR(n) and CHARACTER VARYING(n) are treated as variable-length character strings with an optional length limit. If no length ’n’ is specified, they both default to allowing strings of any length, behaving identically to the TEXT data type. Therefore, from a practical database design perspective within PostgreSQL, the choice between these two keywords is purely a matter of personal preference or adherence to specific coding style guides.

For developers working with PostgreSQL, understanding that VARCHAR and CHARACTER VARYING are interchangeable is a critical piece of knowledge. It eliminates potential concerns about performance differences or compatibility issues between columns defined with either keyword. This allows you to focus on the more important aspects of data modeling, such as choosing appropriate length constraints for your data to maintain data integrity and optimize storage without getting bogged down by a non-existent distinction. This also simplifies migration paths from other SQL databases which might have different internal implementations, as PostgreSQL handles both gracefully.

While VARCHAR and CHARACTER VARYING are identical in PostgreSQL, the broader decision of which string data type to use for a column is vital for efficient database design. The key considerations revolve around data integrity, storage optimization, and clarity for future maintainers. Most commonly, you’ll choose between VARCHAR(n) (or CHARACTER VARYING(n)), TEXT, and less frequently, CHAR(n).

Here’s a breakdown of when to use each, focusing on PostgreSQL’s behavior:

• VARCHAR(n) (or CHARACTER VARYING(n)): This is your workhorse for most variable-length strings where you have a reasonable idea of a maximum length. Examples include names (e.g., VARCHAR(100)), email addresses (e.g., VARCHAR(255)), or product codes (e.g., VARCHAR(20)). The ’n’ constraint is crucial for data validation at the database level, preventing overly long strings from being inserted and ensuring consistency. While it doesn’t save significant storage over TEXT for shorter strings, it provides a valuable integrity check.

• **TEXTQuestion & Answer :
  John uses CHARACTER VARYING in the places where I use VARCHAR. I am a beginner, while he is an expert. This suggests me that there is something which I do not know.

  What is the difference between CHARACTER VARYING and VARCHAR in PostgreSQL?

  VARCHAR is an alias for CHARACTER VARYING, so no difference, see documentation :)

  The notations varchar(n) and char(n) are aliases for character varying(n) and character(n), respectively. character without length specifier is equivalent to character(1). If character varying is used without length specifier, the type accepts strings of any size. The latter is a PostgreSQL extension.

  Note on capitalization: The PostgreSQL documentation uses the all lower case stylization: character varying. In contrast the official SQL standard uses the stylization with all caps throughout its 1000 pages: CHARACTER VARYING.**