PostgreSQL – DATE_PART Function

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In PostgreSQL, the DATE_PART function is used to extract a specific element (e.g., year, month, day, hour, minute, second, etc.) from a date, time, or timestamp value. It returns the numeric value of the specified component.

The basic syntax of the DATE_PART function is as shown below: 

DATE_PART(field, source);

where field is the part of the date or time you want to extract (e.g., ‘year’, ‘month’, ‘day’, ‘hour’, ‘minute’, ‘second’, etc.). The field parameter is case-insensitive, so you can use either uppercase or lowercase letters;

and source is the date, time, or timestamp from which you want to extract the specified field.

Below are some examples of using the DATE_PART function:

  1. Extracting the year from a date:
SELECT DATE_PART('year', '2023-08-06') AS year;

This query will return the year 2023.

  1. Extracting the month from a timestamp:
SELECT DATE_PART('month', TIMESTAMP '2023-08-06 15:30:45') AS month;

This query will return the month 8.

  1. Extracting the day from an interval:
SELECT DATE_PART('day', INTERVAL '5 days') AS days;

This query will return the number of days 5.

  1. Extracting the hour from the current timestamp:
SELECT DATE_PART('hour', CURRENT_TIMESTAMP) AS hour;

This query will return the current hour.

You can use various date and time fields with the DATE_PART function, such as:

  • 'year', 'month', 'day', 'hour', 'minute', 'second': To extract the corresponding elements from the date or timestamp.
  • 'timezone': To extract the time zone from the timestamp.
  • 'epoch': To extract the number of seconds since January 1, 1970 (UNIX epoch time).

Here’s an example of extracting the time zone and epoch from a timestamp: 

SELECT DATE_PART('timezone', TIMESTAMP '2023-08-06 15:30:45') AS timezone, DATE_PART('epoch', TIMESTAMP '2023-08-06 15:30:45') AS epoch;

The DATE_PART function returns numeric values for most components, but it returns text values for certain components, such as the time zone (e.g., 'UTC', 'America/New_York', etc.).

The DATE_PART function is useful when you need to extract specific date and time components in your PostgreSQL queries or perform calculations based on these components.

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