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# How to Not Show Duplicates in SQL To effectively eliminate duplicate records in your database queries, use the powerful COUNT(DISTINCT) function in SQL. This essential function accepts a single argument, specifically the column where you want to count unique values. For example, if you need to count the distinct values in the name column of your database while ensuring optimal performance, implement the following query: ```sql SELECT COUNT(DISTINCT name) FROM table_name; ``` ## Examples Let's explore several practical examples of how this function can be implemented. Consider a table called users containing the following sample data: name | age -----|----- John | 25 Jane | 30 John | 25 Bob | 20 To efficiently count the number of distinct names in this table, execute this optimized query: ```sql SELECT COUNT(DISTINCT name) FROM users; ``` This query returns the value 3, representing the three unique names in the table (John, Jane, and Bob), while automatically handling any duplicate entries. ## How to Not Show Duplicates in SQL To effectively filter out duplicates in your SQL query results, implement the DISTINCT keyword. This powerful feature ensures you receive only unique values from the specified column, improving data clarity and analysis. For instance, to retrieve a clean list of all unique names from the users table, use this optimized query: ```sql SELECT DISTINCT name FROM users ORDER BY name ASC; ``` This enhanced query returns John, Jane, Bob in alphabetical order, presenting only the unique names from the table while maintaining data integrity. ## Additional Info The COUNT(DISTINCT) and DISTINCT functions are widely supported across all major database management systems, including MySQL, PostgreSQL, Oracle, and SQL Server. While the core functionality remains consistent, some advanced features and performance optimizations may vary depending on your specific database platform. For comprehensive guidance and best practices, consult the official documentation of your database system. Remember to consider indexing strategies on frequently queried columns to optimize performance when working with DISTINCT operations on large datasets.