SQL Day Of Week

How can I extract the day of the week from a date in SQL?

Extracting the day of the week from a date is a common task in SQL. Various functions are available depending on the specific database system. This allows for filtering, grouping, and analysis based on the day of the week.

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Description

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Determining the day of the week for a given date is a fundamental task in many database applications. SQL provides functions to achieve this, often leveraging the underlying date and time representation. The specific function and syntax may vary slightly between different database systems (e.g., MySQL, PostgreSQL, SQL Server). Understanding these variations is crucial for writing portable SQL code. For instance, you might need to extract the day of the week to analyze sales trends by day, identify patterns in user activity, or schedule tasks based on the day of the week. The function used to extract the day of the week often returns an integer representing the day (e.g., 1 for Sunday, 2 for Monday, etc.). It's important to consult the documentation for your specific database system to confirm the exact function and integer representation for the day of the week.

Why SQL Day Of Week is important

Knowing how to extract the day of the week from dates is essential for analyzing trends, scheduling tasks, and generating reports in a database. It allows for targeted queries and insights into patterns related to time.

SQL Day Of Week Example Usage


-- MySQL Example
SELECT CURDATE();
SELECT NOW();
SELECT CURRENT_TIMESTAMP;

-- PostgreSQL Example
SELECT CURRENT_DATE;
SELECT CURRENT_TIMESTAMP;

-- SQL Server Example
SELECT GETDATE();
SELECT SYSDATETIME();

SQL Day Of Week Syntax

Common Mistakes

Forgetting to specify the correct function for the specific database system.
Incorrectly interpreting the returned integer value for the day of the week (e.g., assuming 1 is Monday instead of Sunday).
Using the wrong date format in the query.

Frequently Asked Questions (FAQs)

How do I extract the day of the week in MySQL, PostgreSQL, and SQL Server?

In MySQL you can call DAYOFWEEK(date), which returns 1 = Sunday through 7 = Saturday. PostgreSQL offers EXTRACT(DOW FROM date), producing 0 = Sunday through 6 = Saturday; you can also use TO_CHAR(date, 'Day') for the literal name. SQL Server supports DATEPART(dw, date) and DATENAME(dw, date). By default, DATEPART returns 1 = Sunday, but the value shifts when SET DATEFIRST is changed. Always confirm the numbering in your database before using the result in logic or reports.

Why do different databases return different integer values for the same weekday?

The SQL standard does not mandate a specific mapping between weekdays and integers, so each engine chooses its own convention. MySQL starts counting with Sunday = 1, PostgreSQL uses Sunday = 0, and SQL Server’s base value is affected by the DATEFIRST session setting. When you run cross-database analytics, inconsistent mappings can distort results. Normalize the values—or convert them to day names—before comparing datasets from multiple sources.

How can Galaxy help me write portable day-of-week SQL?

Galaxy’s context-aware AI copilot recognizes which database you are connected to and autocompletes the correct date functions. You can ask it to translate a MySQL DAYOFWEEK query into PostgreSQL’s EXTRACT(DOW) or SQL Server’s DATEPART in one click, reducing syntax errors. With Galaxy Collections, teams can endorse a reusable weekday-extraction snippet so everyone runs the same, vetted logic—no more copying SQL into Slack or Notion.