SQL DISTINCT is an essential feature for eliminating duplicate rows in query results. This article offers a quick overview and examples to help you incorporate it into your queries efficiently.
Unique city queries
When querying a table with a large dataset, you may want to find unique entries for a specific column. For example, to get a list of distinct cities from an orders table, you can use.
SELECT DISTINCT city
FROM orders;
Using DISTINCT across columns
To find unique combinations of data from multiple columns, such as customer names, cities, and products, use the following query.
SELECT DISTINCT customername, city, product
FROM orders;
Aggregate function with DISTINCT
DISTINCT can be combined with aggregate functions like COUNT to analyze unique data. For instance, counting unique customers in each city is done with this query.
SELECT city, COUNT(DISTINCT customername) AS UniqueCustomersCount
FROM orders
GROUP BY city;
Filter with WHERE clause
For targeted queries, DISTINCT can be paired with conditions. To get a list of unique customers in New York, use this.
SELECT DISTINCT customername, address, phone
FROM orders
WHERE city = 'New York';
FAQ
What does DISTINCT do?
It ensures unique rows in query results by removing duplicates.
How to use DISTINCT in a query?
Place it after SELECT and specify the columns where duplicates should be removed.
What’s the difference between UNIQUE and DISTINCT?
DISTINCT filters output; UNIQUE enforces constraints on table entries.
Can DISTINCT combine with other clauses?
Yes, it integrates well with WHERE, GROUP BY, and more.
Summary
SQL DISTINCT is a valuable tool for decluttering your database queries and extracting unique insights. By mastering its uses, you’ll improve the efficiency and clarity of your data analysis workflows.
For more examples and practical guidance, explore the full guide SQL DISTINCT: A Comprehensive Guide.
Understanding SQL essentials like DISTINCT ensures a solid foundation for tackling more advanced database challenges.
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