Efficiently Loading CSV Data into Oracle DB: Solving the Merge Problem

In many data-driven environments, we often receive data in CSV format from upstream systems. The challenge lies not just in loading this data into a database, but doing so intelligently: How can we insert new records without duplicating existing ones? How do we handle updates to existing records? How can we track what changed in each load? Can we maintain logs for auditing?

This sounds simple — but if not handled properly, it can lead to duplicate data, inconsistent reports, and untraceable changes.

The Problem When a CSV is loaded daily, it might contain both new rows and updates to existing rows. If we blindly `INSERT`, we violate primary key constraints or create duplicates.

The Solution: MERGE INTO Oracle provides the `MERGE` statement (often called Upsert). It allows us to match records based on a key and then choose to either `UPDATE` or `INSERT`.