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Code Problem / Data Structures and Algorithms / Recursion (32)
Code Problem / Data Structures and Algorithms / Binary Search (30)
Code Problem / Data Structures and Algorithms / Linked Lists (26)
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Code Problem / Data Structures and Algorithms / Hashing (24)
Databases / SQL / Backup and Recovery (19)
Code Problem / Data Structures and Algorithms / Arrays and Strings (19)
Databases / SQL / Database Normalization (18)
Code Problem / Data Structures and Algorithms / Time Complexity (17)
Databases / SQL / Locking (16)
Databases / SQL / Replication (15)
Databases / SQL / SQL Queries (13)
Code Problem / Data Structures and Algorithms / Graphs (13)
Databases / SQL / Database Security (13)
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This problem asks for a SQL query to find all users in a table who have a valid email address.
About this solution: This solution is incomplete because it does not account for email addresses that may have more than one '@' character. A more complete solution would use a regular expression to match email addresses.
This technical problem involves finding the customer with the most orders in a given table. The table consists of customer order information, including customer id, order date, etc. The goal is to write a SQL query to identify the customer with the most orders.
About this solution: The candidate's solution does not demonstrate a level of completeness and does not solve the problem. The candidate's approach is to simply select all data from the customer orders table. This does not provide any information on which customer has the most orders. To solve the problem, the candidate would need to provide a GROUP BY clause to group customer orders by customer ID, and then use a COUNT function to count the number of orders for each customer.
Write a SQL query to find the most recent backup of each database on a server.
About this solution: The candidate's solution does not demonstrate a level of completeness and does not solve the problem. The general approach is not clear.
The table has two columns, id and data. The query should return the data in ascending order of id.
About this solution: The candidate's solution correctly returns the data in the table in ascending order of id. The solution is complete and solves the problem. The approach is straightforward and easy to understand.
This question asks for the 5th highest salary from the "Employees" table. The example input is a table with id, name, and salary columns, and the example output is a table with a salary column.
About this solution: The candidate's solution correctly finds the 5th highest salary from the "Employees" table. The solution uses a with statement to create a rating table, which is then used to select the 5th highest salary. This is a valid approach and the solution correctly solves the problem.
Write a SQL query that returns the total quantity of each product ordered by each customer.
About this solution: The candidate's solution correctly returns the total quantity of each product ordered by each customer. The solution uses the GROUP BY clause to group the customer and product IDs together, and then uses the SUM function to calculate the total quantity for each group. The solution is clear and concise.
None
About this solution: The candidate's solution is correct and demonstrates a good understanding of the game of NIM.
This problem asks you to find the first character in a string that is not repeated elsewhere in the string. For example, given the string "abcdab", the answer would be "c ".
About this solution: The candidate's solution is correct and demonstrates a level of completeness. The candidate's approach is also optimal, as it iterates through the string only once to create the dictionary and then iterates through the string again to find the first character that is not repeated.