How to find duplicate values in a SQL table

Question

Aryan Kumar · Answer

SELECT column1, column2, COUNT(*)

FROM Student

GROUP BY column1, column2

HAVING COUNT(*) > 1;
The HAVING clause is used to filter the groups based on the count value. In this case, we are only returning the groups where the count value is greater than 1, which indicates that there are duplicate values.

You can modify the column names in the SELECT clause and the grouping columns in the GROUP BY clause to fit your specific table structure.

Krishnapriya Rajeev · Answer

To find duplicate values in a SQL table, you can use the GROUP BY clause and the HAVING clause.

Here's an example SQL query that finds duplicate values in a table called my_table, where the duplicates are determined by the combination of columns col1 and col2:

SELECT col1, col2, COUNT(*)
FROM my_table
GROUP BY col1, col2
HAVING COUNT(*) > 1;

This query groups the rows in my_table by combining values in the col1 and col2 columns and counts the number of rows in each group. The HAVING clause filters the groups to only those with a count greater than 1, meaning there are duplicate values in the col1 and col2 columns.

You can modify this query to include additional columns in the output or to use different criteria for determining duplicates, depending on the requirements of your specific use case.

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How to find duplicate values in a SQL table

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