How to Retrieve Only One Copy of Duplicate Records in SQL
Learn how to use SQL SELECT DISTINCT and GROUP BY to get unique records and remove duplicates effectively.
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To get only one copy of duplicate records, use SQL's `SELECT DISTINCT` or specify the columns you want distinct values from with `GROUP BY`. For instance: `SELECT DISTINCT column_name FROM table_name;` or `SELECT column_name FROM table_name GROUP BY column_name;`. This will eliminate duplicates, giving you a unique set of records.
FAQs & Answers
- What is the difference between SELECT DISTINCT and GROUP BY in SQL? SELECT DISTINCT returns unique rows based on specified columns, while GROUP BY groups rows with the same values allowing aggregate functions; both can remove duplicates but have different use cases.
- Can SELECT DISTINCT remove duplicate rows across multiple columns? Yes, SELECT DISTINCT considers all specified columns and returns unique combinations of those columns, effectively removing duplicate rows.
- How do I remove duplicate records permanently from a SQL table? To permanently remove duplicates, you can use DELETE with a subquery or common table expression (CTE) that identifies duplicates based on row identifiers while keeping one unique record.