Efficiently Update and Insert Data Using SQL MERGE Statement

Learn how to use the SQL MERGE statement to `update` and `insert` data consistently between `tables` in Oracle SQL.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: update and insert from another table based on date and column id

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Simplifying Data Management with SQL MERGE

Handling data across multiple tables can be a challenging task, especially when it comes to keeping track of updates and ensuring data integrity. A common scenario is when you want to update records in one table based on the data from another table and also insert new records if they do not yet exist. Fortunately, the SQL MERGE statement offers a powerful solution to this problem.

Problem Overview

Imagine you have two tables: test and test2. Here's a quick look at their structure and some sample data:

Table Structures

test: Contains existing records with an ID, name, and an insertion date.

test2: Holds new records that may either update the existing ones or introduce new entries.

Sample Data

For instance, you might have the following records:

In Table test:

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

In Table test2:

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

The goal is to update the records in test if the insertion_date from test2 is more recent and insert any new records from test2 that do not already exist in test.

Solution: Using SQL MERGE

The best way to tackle this challenge is by using the SQL MERGE statement. This approach allows you to efficiently execute both update and insert operations in a single command. Here’s how you can do it:

Step-by-Step MERGE Command

Basic Structure:
The syntax for the MERGE command is straightforward. You specify the target table (in your case, test) and the source table (test2), along with conditions for matching records.

Formulating the Query:
Below is the MERGE statement you would use to achieve your desired results:

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

Breakdown of the MERGE Statement

MERGE INTO: This specifies the target table (test) that you want to update or where you want to insert new rows.

USING: This clause defines the source table (test2) from which you’ll pull data for updates and inserts.

ON: This condition identifies how to match rows between the two tables (here, matching by id).

WHEN MATCHED: This section specifies what to do when a row in test matches a row in test2. It updates the insertion_date if the test2 date is more recent.

WHEN NOT MATCHED: This part handles cases where there’s no match, inserting new rows into test.

Expected Result

After running the above MERGE command, your test table will be updated and structured as follows:

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

Conclusion

The SQL MERGE statement stands out as an efficient solution for updating and inserting records from one table to another with just one command. It simplifies data management practices and ensures consistency across your databases.

If you're working with Oracle SQL, mastering the MERGE statement can significantly enhance your data-handling capabilities. Happy querying!