C# Algorithms and SQL Online Test
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Sign Up To Use This TestThe C# Algorithms and SQL online test assesses candidates' knowledge of SQL queries and evaluates their algorithmic-thinking skills using C#.
It's an ideal test for pre-employment screening. A good developer should be able to work closely with the database layer and solve back-end problems where any improvement to computational complexity would produce a significantly more efficient solution.
This online test requires candidates to design and analyze algorithms using C# and to write SQL queries that extract, combine, and manipulate data.
Recommended Job Roles
.NET Developer
Back-End Developer
C# Developer
SQL Developer
Web Developer
Sample Candidate Report
Sample Free Questions
Students
3min
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Easy
Easy
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CODE
SQL
Aggregation
Select
Public
SQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Aggregation
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Select
The SELECT statement is used to select data from a database. It is the most used SQL command.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
Given the following data definition, write a query that returns the number of students whose first name is John. String comparisons should be case sensitive.
TABLE students id INTEGER PRIMARY KEY, firstName VARCHAR(30) NOT NULL, lastName VARCHAR(30) NOT NULL
Enrollment
5min
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Easy
Easy
-
CODE
SQL
Conditions
Update
Public
SQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditions
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
Update
The UPDATE statement is used to modify the existing records in a table and is one of the most used operations for working with the database.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
A table containing the students enrolled in a yearly course has incorrect data in records with ids between 20 and 100 (inclusive).
TABLE enrollments id INTEGER NOT NULL PRIMARY KEY year INTEGER NOT NULL studentId INTEGER NOT NULL
Write a query that updates the field 'year' of every faulty record to 2015.
Alert Service
10min
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Easy
Easy
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CODE
C#
Interfaces
Inversion of control
Refactoring
Public
C#
The C# programming language is a simple, modern, general-purpose, object-oriented programming language. Having a basic familiarity with the programming language used on the job is a prerequisite for quickly getting up to speed.
Interfaces
An interface is used to define an abstract type that defines behaviors as method signatures. Instances of different types can implement the same interface and provide a way for a developer to reuse the code.
Inversion of control
Inversion of Control (IoC) is a pattern that is used to invert different kinds of controls in object-oriented design to achieve loose coupling. Developers should know how to use it in order to increase modularity of the program and make it extensible.
Refactoring
The process of restructuring existing computer code without changing its external behavior. It is essential for keeping code readable and maintainable.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
Refactor the AlertService and AlertDAO classes:
- Create a new interface, named IAlertDAO, that contains the same methods as AlertDAO.
- AlertDAO should implement the IAlertDAO interface.
- AlertService should have a constructor that accepts IAlertDAO.
- The RaiseAlert and GetAlertTime methods should use the object passed through the constructor.
Premium Questions
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Questions
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SQLSQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditions
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
Views
A database view is a result set that is defined by a stored query, the results of which can can also be queried. As a fundamental and widely used database construct, it's useful for candidates to understand how and when they should be used.
C#
The C# programming language is a simple, modern, general-purpose, object-oriented programming language. Having a basic familiarity with the programming language used on the job is a prerequisite for quickly getting up to speed.
Algorithmic thinking
When designing and/or analyzing an algorithm or data structure, it is important to consider the performance and structure of an implementation. Algorithmic thinking is one of the key traits of a good programmer, especially one working on complex or performance-critical code.
Arrays
An array is a container of a fixed number of objects of a similar type. It is a fundamental component of most programming languages.
Data structures
Choosing the right data structure to solve a problem can have huge implications on the performance of an application. Knowing when to use a specific data structure is one of the most important skills for a programmer.
Subqueries
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
Update
The UPDATE statement is used to modify the existing records in a table and is one of the most used operations for working with the database.
Sorting
Every programmer should be familiar with data-sorting methods, as sorting is very common in data-analysis processes.
Constraints
Constraints are used to define rules and relationships. They are applied to a dataset. A constraint may take many forms, such as x ≤ 5 in a programming language and a NOT NULL constraint in a SQL table definition.
Create table
The CREATE TABLE statement is used to create a new table in a database. It is an essential command when creating new database.
Database schema
A database schema defines how data is stored in a database. An SQL database uses a schema to define tables consisting of rows and columns that use fixed data types to store data. Formalizing how data is stored is the first step towards building an application or service.
Select
The SELECT statement is used to select data from a database. It is the most used SQL command.
Create index
The CREATE INDEX statement is used to create indexes for tables. Indexes are used to retrieve data from the database more quickly. They are very important for making performant queries.
Performance tuning
The performance of an application or system is important. The responsiveness and scalability of an application are all related to how performant an application is. Each algorithm and query can have a large positive or negative effect on the whole system.
Alter table
The ALTER TABLE statement is used to add, delete, or modify columns and constraints in an existing table. Alter table statements are important for all programmers who have to modify existing schemas.
Aggregation
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Ordering
Knowing how to order data is a common task for every programmer.
Insert
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
Left join
LEFT JOIN is one of the ways to merge rows from two tables. We use it when we also want to show rows that exist in one table, but don't exist in the other table.
Bug fixing
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
Queue
A queue is a collection of items that are maintained in a sequence and can be modified by the addition of entities at one end of the sequence and removal from the other end of the sequence. It is the collection to be used when first-in-first-out (FIFO) collection is needed.
Indexes
The proper implementation and use of indexes are important for improving the performance of database queries.
Union
The UNION operator is used to combine the result-set of two or more SELECT statements. It is often used when a report needs to be made based on multiple tables.
Group by
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
Joins
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
Tree
A tree is a hierarchical structure defined recursively starting with the root node, where each node is a data structure consisting of a value, together with a list of references to other nodes (the "children"). A lot of problems can be solved efficiently with trees, which makes them important for developers.
Linked list
A linked list is a linear collection of data elements where each element points to the next. It is a data structure consisting of a collection of nodes which together represent a sequence. It is usually used for advanced scenarios where we need fast access to the next element, or when we need to remove an element from anywhere in the collection.
StringBuilder
Since a string is an immutable data structure, concatenating multiple strings can introduce significant performance penalties. Every experienced developer should know when to use StringBuilder instead of simply concatenating two strings to improve performances in such scenarios.
Strings
The string data structure is used to represent text. It is one of the most commonly used data structures. Therefore, every programmer should be skilled at string manipulation.
Dictionary
A dictionary (or associative array) is a data type composed of a collection of key-value pairs, where each possible key appears at most once in the collection. It is used when we need to access items by their keys.
SQL CASE
The CASE statement is SQL's control statement. It goes through conditions and returns a value.
CTE
A CTE (Common Table Expression) is a temporary result set that can be referenced within another SELECT, INSERT, UPDATE, or DELETE statement. Recursive CTEs can reference themselves, which enables developers to work with hierarchical data.
Delete
The delete statement is used to delete records in a table and is one of the four basic CRUD functions (create, read, update, and delete) required for working with any persistent storage.
Graphs
Many real-life situations are best modeled by graphs. Therefore, an in-depth knowledge of graph data structures is important for a good programmer.
HashSet
HashSet is container that stores unique elements in no particular order. This allows for fast checks to see if a value was already added.
Score Distribution
# of candidates
| 0-33% | |
|---|---|
| 34-66% | |
| 67-100% |
Score