How Can I Find and Count Duplicate Values in an Oracle Table?

Identifying and Counting Duplicate Records in Oracle Tables

Maintaining data integrity and database performance in large Oracle databases requires efficient methods for detecting and managing duplicate records. Oracle SQL offers powerful tools to accomplish this.

SQL Query for Finding Duplicate Values

The following SQL statement effectively identifies duplicate values and their frequency within an Oracle table:

<code class="language-sql">SELECT column_name, COUNT(*) AS duplicate_count
FROM table_name
GROUP BY column_name
HAVING COUNT(*) > 1;</code>

Illustrative Example: Duplicate JOB_NUMBERs

Let's assume a "JOBS" table with a "JOB_NUMBER" column. To pinpoint duplicate JOB_NUMBERs and their counts, use this query:

<code class="language-sql">SELECT JOB_NUMBER, COUNT(*) AS duplicate_count
FROM JOBS
GROUP BY JOB_NUMBER
HAVING COUNT(*) > 1;</code>

This query will list all JOB_NUMBERs appearing more than once, along with their occurrence counts. This information is crucial for identifying and addressing duplicate records, enabling further analysis or data cleansing operations.

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