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This technical problem deals with writing a SQL query to find the number of distinct values in each column of a table. The input is a table with two columns, and the output is the number of distinct values in each column.

About this solution: The solution above is optimal because it uses the COUNT function with the DISTINCT keyword. This will count the number of unique values in each column.

Write a SQL query to find employees who have been with a company for more than 5 years. The table to query has the following schema: (name, department, start_date). The query should return the (name, department, start_date) for each employee meeting the 5 year criteria.

About this solution: This solution is correct and demonstrates a good understanding of SQL.

The function should take a list of integers as input and return the sum of the even integers in the list.

About this solution: This solution is optimal because it uses a generator expression to filter the list and sum the even numbers. This is optimal because it is a single pass through the list, and it does not require any additional memory. It is also very readable.

Write a SQL query to find all pairs of rows (a, b) such that a is in table A, b is in table B, and a and b have the same value for column C.

About this solution: This solution is correct and demonstrates a good understanding of SQL. The approach is straightforward and easy to follow.

This problem deals with finding the sum of all integers in a list that are greater than or equal to 10. An example input is given, as well as the expected output.

About this solution: The candidate's solution correctly solves the problem and returns the sum of the integers that are greater than or equal to 10. The candidate's approach is to iterate through the list and add the integers that are greater than or equal to 10 to a sum variable. This is a valid approach and the candidate's solution is complete.

The technical problem is how to write a SQL query that returns the top 3 most populous countries. The example output is China, India, United States.

About this solution: The solution is optimal because it uses the ORDER BY and LIMIT clauses to sort the table by population in descending order and then limit the results to the top 3.

This Python function takes a list of integers as input and returns the largest number in the list.

About this solution: The candidate's solution correctly finds the largest number in the list. The candidate could have used the built-in max() function to find the largest number in the list.

Write a SQL query to find the top 10 customers by total spent.

About this solution: The solution is optimal because it uses the ORDER BY and LIMIT clauses to sort the table by total_spent in descending order and then limit the results to the top 10 customers.