How to Find and Count Duplicate Values in an Oracle Table?

Identify duplicate values ​​in Oracle table

Looking up duplicate values ​​in tables is critical for data integrity and analysis. In Oracle, this task can be accomplished using simple SQL statements combined with aggregate functions and HAVING clauses.

SQL statement to identify duplicate values

The following SQL statement retrieves duplicate values ​​and their number of occurrences from a given column in an Oracle table:

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

Segmentation:

The
• SELECT clause extracts column_name and counts the distinct occurrences of count.
The
• FROM clause specifies the table_name from which data will be retrieved.
The
• GROUP BY clause groups the results by column_name, effectively counting the occurrences of each distinct value.
The
• HAVING clause filters the aggregation results and only displays values ​​with a count greater than 1, indicating duplicates.

Example:

Consider a table called JOBS that contains a column called JOB_NUMBER. To identify duplicate JOB_NUMBER, execute the following statement:

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

This query will return all distinct JOB_NUMBERs that occur more than once in the table, along with the number of times they occur.

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