How to carry out complex queries and subqueries in Hive

5 months ago

2 minutes

Executing complex queries and subqueries in Hive can be achieved by using the HiveQL language. HiveQL is similar to SQL and can be used to write complex query statements.

Here are some examples of complex queries and subqueries.

Find the name of the product with the highest sales using a subquery.

SELECT product_name 
FROM products 
WHERE product_id = (
    SELECT product_id 
    FROM sales 
    GROUP BY product_id 
    ORDER BY sum(sales_amount) DESC 
    LIMIT 1
);

Calculate the total sales for each department by using JOIN and aggregate functions.

SELECT department_name, sum(sales_amount) as total_sales
FROM sales
JOIN departments ON sales.department_id = departments.department_id
GROUP BY department_name;

Classify sales amount using a CASE statement.

SELECT 
    product_name,
    CASE 
        WHEN sales_amount < 1000 THEN 'Low'
        WHEN sales_amount >= 1000 AND sales_amount < 5000 THEN 'Medium'
        ELSE 'High'
    END AS sales_category
FROM sales;

These examples demonstrate how to use complex queries and subqueries in Hive to manipulate data. By combining various querying techniques, you can perform a variety of complex data analysis and processing tasks.