SQL queries to retrieve the first date of the current month and the last date of the previous month are commonly used in various data analysis and reporting tasks. These dates are essential for calculating time periods, generating reports, and performing other date-related operations. In this article, we will explore different SQL methods to achieve this goal and provide you with the necessary code snippets to get the current month first date and last month end date.
The first date of the current month can be obtained using the SQL functions that extract the first day of the month from the current date. Similarly, the last date of the previous month can be calculated by finding the last day of the previous month. Here are a few SQL methods to achieve this:
1. Using the `DATE_TRUNC` function:
The `DATE_TRUNC` function is available in some SQL databases like PostgreSQL and Redshift. It truncates a timestamp to a specified precision and returns the truncated timestamp. To get the first date of the current month, you can use the following query:
“`sql
SELECT DATE_TRUNC(‘month’, CURRENT_DATE) AS first_date_of_current_month;
“`
To get the last date of the previous month, you can use the following query:
“`sql
SELECT DATE_TRUNC(‘month’, CURRENT_DATE – INTERVAL ‘1 month’) + INTERVAL ‘1 day’ – INTERVAL ‘1 second’ AS last_date_of_previous_month;
“`
2. Using the `EXTRACT` function:
The `EXTRACT` function is available in many SQL databases and can be used to extract specific parts of a timestamp, such as year, month, or day. To get the first date of the current month, you can use the following query:
“`sql
SELECT CURRENT_DATE – INTERVAL ‘1 day’ (EXTRACT(DAY FROM CURRENT_DATE) – 1) AS first_date_of_current_month;
“`
To get the last date of the previous month, you can use the following query:
“`sql
SELECT (CURRENT_DATE – INTERVAL ‘1 day’) – INTERVAL ‘1 month’ + INTERVAL ‘1 day’ AS last_date_of_previous_month;
“`
3. Using the `LAST_DAY` function:
The `LAST_DAY` function returns the last day of the month for a given date. To get the last date of the previous month, you can use the following query:
“`sql
SELECT LAST_DAY(CURRENT_DATE – INTERVAL ‘1 month’) AS last_date_of_previous_month;
“`
To get the first date of the current month, you can use the following query:
“`sql
SELECT CURRENT_DATE – INTERVAL ‘1 day’ (EXTRACT(DAY FROM CURRENT_DATE) – 1) AS first_date_of_current_month;
“`
These methods can be used to retrieve the current month first date and last month end date in various SQL databases. Depending on the database you are using, you may need to adjust the functions and syntax accordingly. By understanding these methods, you can efficiently perform date-related operations in your SQL queries.
