How Can I Efficiently Generate a Date Range in SQL for the Past Year?

Generating a Date Range using SQL Query

When working with SQL databases, fetching data for specific time ranges is a common task. Imagine having a SQL query that requires a date parameter and the need to execute it repeatedly for each day of the past year. To avoid manually entering each date, generating a dynamic list of dates is necessary.

One approach is to create a numerical list (0 to 364) and manipulate the dates using the SQL function SYSDATE. However, a more efficient method exists, eliminating the need for large tables or intermediate calculations.

Consider the following SQL query:

SELECT TRUNC (SYSDATE - ROWNUM) dt
FROM DUAL CONNECT BY ROWNUM < 366

This query leverages the power of SQL's CONNECT BY clause, which recursively generates rows based on a specified condition. In this case, the condition is ROWNUM < 366, which ensures that 366 rows are generated.

Each row represents a date, starting from the current day SYSDATE and subtracting the ROWNUM value. The TRUNC function simplifies the date to include only the day, month, and year components, excluding any time information.

As a result, this query produces a list of 365 distinct dates, representing every day of the past year, which can be conveniently used as parameters for the desired SQL query. This technique streamlines the date generation process and eliminates the need for cumbersome manual entry or additional table lookups.

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