Creating Date Ranges from Day-Based Data Using Oracle SQL

Creating Date Ranges from Day-Based Data in Oracle SQL

In this article, we will explore how to create date ranges from day-based data using Oracle SQL. We will use a real-world example of daily data and demonstrate how to extract the desired output using various techniques.

Problem Statement

We are given a table with three columns: id, date, and value. The date column represents the date of each entry, and the value column represents the corresponding value. We need to create a new table with three additional columns: date_from, date_until, and value. The date_from column should contain the earliest date for each group of consecutive dates, the date_until column should contain the latest date for each group of consecutive dates, and the value column should be the maximum value for each group of consecutive dates.

Sample Data

Let’s use the following sample data to demonstrate our example:

id     date     value
1      01.08.22 a
1      02.08.22 a
1      03.08.22 a
1      04.08.22 b
1      05.08.22 b
1      06.08.22 a
1      07.08.22 a
2      01.08.22 a
2      02.08.22 a
2      03.08.22 c
2      04.08.22 a
2      05.08.22 a

Desired Output

The desired output is:

id     date_from     date_until    value
1      01.08.22      03.08.22      a
1      04.08.22      05.08.22      b
1      06.08.22      07.08.22      a
2      01.08.22      02.08.22      a     
2      03.08.22      03.08.22      c
2      04.08.22      05.08.22      a

Solution

To solve this problem, we can use a combination of the ROW_NUMBER() function and grouping techniques in Oracle SQL.

Using ROW_NUMBER()

The first step is to assign a unique number to each row within each group of consecutive dates using the ROW_NUMBER() function. We will do this by partitioning the table by id and ordering the rows by date.

SELECT 
    t1.id,
    t1.date,
    t1.value,
    ROW_NUMBER() OVER(PARTITION BY t1.id ORDER BY t1.date) AS rn
FROM yourtable t1;

Calculating Date Ranges

Next, we will calculate the date_from and date_until values by subtracting the rn from the rn + 1. This will give us the number of days between consecutive dates.

SELECT 
    id,
    MIN(date) AS date_from,
    MAX(date) AS date_until,
    value
FROM (
    SELECT 
        t1.id,
        t1.date,
        t1.value,
        ROW_NUMBER() OVER(PARTITION BY t1.id ORDER BY t1.date) - 
        ROW_NUMBER() OVER(PARTITION BY t1.id, t1.value ORDER BY t1.date) AS rn
    FROM yourtable t1
) 
GROUP BY id, rn;

Handling Ties

In the above query, we are assuming that there are no ties in the date column. However, if there are ties, we need to handle them separately. One way to do this is by using the DENSE_RANK() function instead of ROW_NUMBER(). The DENSE_RANK() function assigns the same rank to tied elements.

SELECT 
    id,
    MIN(date) AS date_from,
    MAX(date) AS date_until,
    value
FROM (
    SELECT 
        t1.id,
        t1.date,
        t1.value,
        DENSE_RANK() OVER(PARTITION BY t1.id ORDER BY t1.date) - 
        DENSE_RANK() OVER(PARTITION BY t1.id, t1.value ORDER BY t1.date) AS rn
    FROM yourtable t1
) 
GROUP BY id, rn;

Fiddle Example

You can try the above query in a fiddle environment to see the results.

<p>See <a href="https://db<>fiddle.org/">db<>fiddle</a></p>

Conclusion

In this article, we demonstrated how to create date ranges from day-based data using Oracle SQL. We used a combination of ROW_NUMBER() and grouping techniques to achieve the desired output. By understanding how to handle ties and calculate date ranges, you can solve similar problems in your own projects.

Last modified on 2024-08-10