How to Filter Two Years Ago From Current Date In Postgresql?

In PostgreSQL, you can filter records from two years ago from the current date by using the DATE_TRUNC function to truncate the current date to the year, subtracting two years, and then filtering records based on this calculated date. Here is an example query:

SELECT * FROM your_table WHERE date_column >= DATE_TRUNC('year', CURRENT_DATE) - INTERVAL '2 years' AND date_column < DATE_TRUNC('year', CURRENT_DATE) - INTERVAL '1 year';

This query filters records where the date_column is between two years ago and one year ago from the current date.

What is the EXTRACT function in PostgreSQL and how can it be used to extract specific date components?

The EXTRACT function in PostgreSQL is used to extract specific date components, such as year, month, day, hour, minute, etc., from a timestamp or interval value.

The syntax of the EXTRACT function is as follows:

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EXTRACT(field FROM source)

Where:

• field is the date part that you want to extract, such as YEAR, MONTH, DAY, HOUR, MINUTE, etc.
• source is the timestamp or interval value from which you want to extract the date part.

For example, if you want to extract the year and month from a timestamp value, you can use the following query:

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SELECT EXTRACT(YEAR FROM '2022-03-14 12:34:56') AS year,
       EXTRACT(MONTH FROM '2022-03-14 12:34:56') AS month;

This will return:

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| year | month |
|------|-------|
| 2022 | 3     |

You can also use the EXTRACT function in conjunction with other SQL functions and clauses to perform more complex date operations.

What is the AGE function in PostgreSQL and how can it be used to calculate date differences?

In PostgreSQL, the AGE function calculates the difference between two dates or timestamps. It returns the interval between two dates in the form of years, months, and days.

The AGE function can be used in the following format to calculate the difference between two dates:

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SELECT AGE(end_date, start_date) AS date_difference

For example, if you have a table orders with columns order_date and ship_date, you can calculate the age of each order by using the AGE function:

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SELECT AGE(ship_date, order_date) AS order_age
FROM orders

This will return the age of each order in years, months, and days.

How to filter records from two years ago using date ranges in PostgreSQL?

To filter records from two years ago in PostgreSQL using date ranges, you can use the following query:

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SELECT *
FROM your_table_name
WHERE your_date_column >= date_trunc('year', current_date - interval '2 year') 
AND your_date_column < date_trunc('year', current_date - interval '1 year');

Replace your_table_name with the name of your table and your_date_column with the name of the column that contains the date you want to filter on.

In this query, we are using the date_trunc function to truncate the current date to the beginning of the year and then subtracting 2 years to get the date range for two years ago. We are then filtering records where the date column is greater than or equal to the beginning of that year and less than the beginning of the next year (i.e., two years ago).

This query will retrieve all records from two years ago from your specified table.