Duplicate rows can clutter your query results, making data analysis difficult. PostgreSQL's DISTINCT clause provides a simple solution for ensuring that your results contain only unique entries. This article offers a quick overview of how to implement DISTINCT in your queries.
Quick guide to PostgreSQL DISTINCT
The SELECT DISTINCT clause helps you eliminate duplicate rows from your results. The basic syntax is:
SELECT DISTINCT column1, column2
FROM table_name;
Single Column
To get unique values from one column:
SELECT DISTINCT column1
FROM table_name;
Multiple Columns
For unique combinations of multiple columns:
SELECT DISTINCT column1, column2
FROM table_name;
FAQ
What does DISTINCT do in PostgreSQL?
It removes duplicate rows, ensuring that each result is unique.
How do I apply DISTINCT?
Use it after SELECT in your query, followed by the columns you wish to be unique.
Can DISTINCT be used with several columns?
Yes, it will return rows where the combination of specified columns is unique.
Does DISTINCT sort the data?
No, DISTINCT only removes duplicates. Sorting is done separately using ORDER BY.
Conclusion
Using PostgreSQL's DISTINCT clause is an effective way to ensure your query results are free from duplicates. For more details and examples, check out the complete guide PostgreSQL DISTINCT: Removing Duplicate Rows from a Result Set.
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