#join

Find the error in the provided SQL query.

Given a CSV file with raw customer transactions, design an ETL pipeline that cleans data, aggregates total sales by region and product, and loads into target table

Given a complex nested query, how would you refactor it for better readability and efficiency?

Given a table with 10 records and another with 4 records, how many records result from a cross join?

Given a table with sales data, write a query to find consecutive days with decreasing revenue.

Given an unoptimized query execution plan, how would you diagnose and improve performance?

Given the data below, explain the results of different types of joins: Inner Join, Left Join, Right Join. Will a schema be created?

Given two dataframes (df1: id, name and df2: id, country, address, city, count), join them, filter for rows where country = 'Singapore', and pivot the output. Sort cities in descending order of population count