## Replication

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Check these solutions from our community:
Databases / SQL DifficultyHard SQL
You are given two tables, Table A and Table B. Your task is to write a SQL query that returns the sum of the values in Table A, multiplied by the sum of the values in Table B.
About this solution: This solution is correct and demonstrates a level of completeness. It correctly calculates the sum of the values in table A and table B, and then multiplies them together.
Jan 30
Databases / SQL DifficultyHard SQL
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.
Jan 28
Databases / SQL DifficultyHard SQL
To replicate a database across multiple servers, you would need to set up a master server with the database, and then set up replication on the other servers. This would allow the other servers to have copies of the database, which would be updated whenever the master server's database is updated.
About this solution: The candidate's solution is incomplete. It does not address how to keep the databases in sync or how to handle write conflicts. Additionally, the candidate does not mention any performance implications of this solution.
Jan 27
Write a SQL query that returns the top 10 customers by total spent.
About this solution: This solution is correct and demonstrates a level of completeness. The approach is straightforward and easy to follow.
Jan 21
Databases / SQL DifficultyMedium SQL
This technical problem involves writing a SQL query to find the total number of items ordered for each order in a database. The database consists of two tables, "orders" and "order_items ". The "orders" table includes the order_id for each order, while the "order_items" table includes the order_id and the number of items ordered for that particular order. The expected output is a table that lists the order_id and the total number of items ordered for each order.
About this solution: The candidate's solution is incomplete and does not solve the problem. The general approach is not clear.
Nov 30
Databases / SQL DifficultyHard SQL
This technical problem asks the reader to write a SQL query to find the average order value for each customer, given a table of customer orders. An example input and output is provided.
About this solution: The solution above is optimal because it uses the GROUP BY clause to group the orders by customer_id, and then uses the AVG function to calculate the average order value for each customer.
Nov 26
Databases / SQL DifficultyHard SQL
The problem is asking for the id of the row with the maximum value in a table with two columns, "id" and "value". An example input and output is given.
About this solution: The candidate's solution is correct and demonstrates a good understanding of SQL. The solution is also efficient, as it only requires one pass through the table.
Nov 25
Databases / SQL DifficultyHard SQL
This technical problem deals with writing a SQL query to find all parents who have at least one child. The example input and output are provided in the body of the problem.
About this solution: The candidate's solution is correct and demonstrates a good understanding of SQL. The solution is also efficient, using a JOIN to combine the two tables and then using DISTINCT to remove any duplicate rows.
Nov 24