, Max Sum
, Paper Strip
, Unloading Trucks
, ATM Locations
, Ban Users
, Bank Branches
, Cheapest Product
, Department Report
, Employee Manager
, Hospital Patients
, Index Performance
, Menu Items
, Merge Stock Index
, Movies Live
, Restaurant Menu
, SMS Messages
, Student Activities
, Student Max Score
, Youngest Child
, Internal Nodes
, Book Sale
, Remove Repetitions
, Unique Product
, Unique Numbers
, Moving Total
, Student Rankings
, Average Salary
, Welfare Organization
, Auto Show
, Movie Genres
, Manager Sales
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.
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.
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
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.
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.
The Java 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.
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.
Many real-life situations are best modeled by graphs. Therefore, an in-depth knowledge of graph data structures is important for a good programmer.
An array is a container of a fixed number of objects of a similar type. It is a fundamental component of most programming languages.
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.
Every programmer should be familiar with data-sorting methods, as sorting is very common in data-analysis processes.
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.
The CREATE TABLE statement is used to create a new table in a database. It is an essential command when creating new database.
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.
The SELECT statement is used to select data from a database. It is the most used SQL command.
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.
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.
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.
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.
Knowing how to order data is a common task for every programmer.
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
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.
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
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.
The proper implementation and use of indexes are important for improving the performance of database queries.
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.
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
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.
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.
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.
A HashMap (or dictionary) 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.
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.
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.
HashSet is container that stores unique elements in no particular order. This allows for fast checks to see if a value was already added.
The CASE statement is SQL's control statement. It goes through conditions and returns a value.
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.