how to change date format in sql

3 min read 24-01-2025

Dates and times are fundamental in many database applications. But SQL databases don't inherently store dates in a specific display format. The format you see depends on your SQL client, the database system itself (MySQL, PostgreSQL, SQL Server, etc.), and sometimes even your operating system settings. This article will guide you through changing how dates are displayed in various SQL dialects. We'll focus on retrieving dates in a custom format, not altering the underlying data storage.

Understanding Date Storage vs. Display

It's crucial to understand that SQL databases typically store dates internally as numbers or a specific internal format. The format you see when querying data is simply how the database presents that internal representation. You're not changing how the date is stored, just how it's shown.

Common SQL Date Formatting Functions

Most SQL databases offer functions to convert date and time values into different string representations. These functions typically take the date/time value as input and a format string that specifies the desired output. The specifics of the format string syntax vary between database systems.

MySQL

MySQL uses the DATE_FORMAT() function for this purpose.

Example:

SELECT DATE_FORMAT(order_date, '%Y-%m-%d') AS formatted_date
FROM orders;

This query retrieves the order_date column and formats it as 'YYYY-MM-DD'. Here's a breakdown of common format specifiers:

%Y: Four-digit year
%m: Two-digit month (01-12)
%d: Two-digit day (01-31)
%M: Full month name (January, February, etc.)
%b: Abbreviated month name (Jan, Feb, etc.)
%H: Hour (00-23)
%i: Minute (00-59)
%s: Second (00-59)

PostgreSQL

PostgreSQL uses the to_char() function. Its format codes are slightly different.

Example:

SELECT to_char(order_date, 'YYYY-MM-DD') AS formatted_date
FROM orders;

PostgreSQL's to_char() function offers a wide range of formatting options, including those for different locales and custom separators. Consult the PostgreSQL documentation for a complete list.

SQL Server

SQL Server uses the CONVERT() or FORMAT() functions. FORMAT() is available from SQL Server 2012 onwards.

Example (CONVERT):

SELECT CONVERT(VARCHAR(10), order_date, 120) AS formatted_date
FROM orders;

Style 120 in CONVERT represents the 'YYYY-MM-DD' format. Other styles are available for different formats.

Example (FORMAT):

SELECT FORMAT(order_date, 'yyyy-MM-dd') AS formatted_date
FROM orders;

FORMAT offers greater flexibility and control over the format string than CONVERT.

Other Database Systems

Other database systems (Oracle, SQLite, etc.) have their own date formatting functions. Refer to the documentation for your specific database for details.

How to Choose the Right Date Format

The best date format depends heavily on your application's needs and your target audience. Consider these factors:

Internationalization: Use formats that are commonly understood in your target regions.
Data Analysis: For data analysis, YYYY-MM-DD or YYYYMMDD is generally preferred for easy sorting and filtering.
User Experience: For user interfaces, formats like "Month DD, YYYY" or "DD Mon YYYY" might be more readable.
Data Exchange: If you're exchanging data with other systems, ensure compatibility through a standardized format.

Example: Formatting Dates with Time

Let's extend the examples to include time information.

MySQL:

SELECT DATE_FORMAT(order_timestamp, '%Y-%m-%d %H:%i:%s') AS formatted_timestamp
FROM orders;

PostgreSQL:

SELECT to_char(order_timestamp, 'YYYY-MM-DD HH24:MI:SS') AS formatted_timestamp
FROM orders;

SQL Server (FORMAT):

SELECT FORMAT(order_timestamp, 'yyyy-MM-dd HH:mm:ss') AS formatted_timestamp
FROM orders;

Remember to replace order_date or order_timestamp with the actual name of your date/time column. Always consult the documentation of your specific SQL database system for the complete list of supported date and time format codes. Careful selection of these codes ensures clarity and efficiency in your SQL queries.