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Asked: 2024-09-26T21:48:28+05:30 In:

how to select distinct rows in sql

Hi, I hope you can help me with a SQL issue I’m facing. I’m currently working on a project that involves querying a database to extract some specific data, but I’ve stumbled upon a problem with duplicate rows in my results. I want to select distinct rows to ensure that each entry in my output is unique, as duplicates are causing confusion and making it difficult to analyze the data properly.

I’ve read that using the `DISTINCT` keyword can help eliminate these duplicate entries, but I’m not entirely sure how to implement it correctly in my SQL query. Does it apply to all columns, or do I need to specify which columns I want to be distinct? Additionally, I’m unsure how this might impact performance, especially if I’m working with a large dataset.

Could you please clarify how to use the `DISTINCT` keyword effectively and any considerations I should keep in mind while implementing it? Any examples or best practices would be greatly appreciated! Thank you!

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    2 Answers

    1. How to Select Distinct Rows in SQL

      So, like, if you’re trying to get only the different rows from your database and not all the duplicates, you can use this cool thing called SELECT DISTINCT. It’s super easy!

      Here’s how you can do it:

      SELECT DISTINCT column_name
FROM table_name;

      Just replace column_name with what you wanna see and table_name with where it’s at. Like if you have a table named “customers” and you’re interested in unique “city” names, it’d look like:

      SELECT DISTINCT city
FROM customers;

      This will give you a list of all the different cities in your “customers” table without repeating any of them. Awesome right?

      If you wanna get distinct rows based on more than one column, you can just add more column names separated by a comma. Like:

      SELECT DISTINCT column1, column2
FROM table_name;

      So, if you want unique combinations of city and state, just do:

      SELECT DISTINCT city, state
FROM customers;

      Remember, it’s a great way to clean up your data when you’re working with messy tables! Just keep it simple, and you’ll get the hang of it in no time!


    2. To select distinct rows in SQL, you can utilize the `DISTINCT` keyword in your `SELECT` statement. This is particularly useful when dealing with large datasets where redundancy might skew analysis. For example, if you have a table named `employees` and you want to retrieve unique job titles, you would execute a query like `SELECT DISTINCT job_title FROM employees;`. This command will return a list of distinct job titles without any duplicates, ensuring that your resultant dataset maintains integrity.

      Alternatively, if you want to select distinct combinations of multiple columns, you can specify them all within the `DISTINCT` clause. For instance, `SELECT DISTINCT first_name, last_name FROM employees;` will yield unique pairs of first and last names. It’s important to remember that the distinctness applies to the entire row of specified columns; thus, only identical rows across all columns will be eliminated. Additionally, leveraging other SQL functions like `GROUP BY` can also help achieve similar outcomes while allowing for aggregation. Always ensure to tailor your queries to the specific requirements of your dataset for optimal results.

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