How to Fetch the Latest Records Based on Two Columns in Oracle SQL

Learn how to efficiently retrieve the latest records based on `SYS_UPDATE_DATE` and `SYS_CREATION_DATE` using Oracle SQL.
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How to Fetch the Latest Records Based on Two Columns in Oracle SQL

When working with data in SQL, there often arises a need to query records based on multiple conditions or columns. One common scenario is needing to fetch the latest records considering two different date columns. This guide will guide you through how to achieve this specifically in Oracle SQL.

The Problem

Given a dataset that tracks subscriptions, our goal is to select the most recent records based on the following criteria:

If multiple entries exist for a SUBSCRIBER_NO and share the same SYS_UPDATE_DATE, we want to select the record with the latest SYS_CREATION_DATE.

When a SUBSCRIBER_NO has records with different SYS_UPDATE_DATE values, we should retrieve the record with the latest SYS_UPDATE_DATE.

Example Data

Consider the following dataset for reference:

SUBSCRIBER_NOCUSTOMER_IDSYS_CREATION_DATESYS_UPDATE_DATEOPERATOR_ID6168620919904164019-JUN-2219-JUN-226113163786168620914578164524-AUG-2019-JUN-226113163786168621019904456719-JUN-2219-JUN-226113163796168621014578123424-AUG-2017-JUN-22611316379The expected output from this data should yield:

SUBSCRIBER_NOCUSTOMER_IDSYS_CREATION_DATESYS_UPDATE_DATEOPERATOR_ID6168620919904164019-JUN-2219-JUN-226113163786168621019904456719-JUN-2219-JUN-22611316379The Solution

To achieve the desired result, we can leverage the SQL ROW_NUMBER() function combined with a subquery. The ROW_NUMBER() function allows us to assign a unique sequential integer to rows within a partition of a result set.

Here’s a step-by-step breakdown of how to write the SQL query:

Step 1: Understand the Syntax

We will utilize a nested query to first select the relevant columns and apply the ROW_NUMBER() function.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Explanation of the Query

Subquery: We create a subquery to select the necessary columns.

ROW_NUMBER(): This function partitions the results by SUBSCRIBER_NO, ordering first by SYS_UPDATE_DATE in descending order and then by SYS_CREATION_DATE in descending order.

Filtering: Finally, we filter the results using WHERE subselect.RN=1 to get only the latest records.

Conclusion

Using this approach, you can effectively fetch the latest records based on the criteria set by two date columns. This method is not only efficient but also takes advantage of SQL's powerful window functions. With this query, you can easily adapt it to suit varying datasets and requirements as needed.

Feel free to reach out if you have any further questions or need assistance with any SQL-related topics!