, Index Performance
, Employee Manager
, Merge Stock Index
, Cheapest Product
, Movies Live
, Bind Variables
, Merge Lists
, Insert Employee
, Query Performance
, Lap Times
, Remove Element
, ATM Locations
, Ban Users
, Department Report
, Delete Orders
, Restaurant Menu
, Student Activities
, Hospital Patients
, Bank Branches
, Menu Items
, User Statistics
, Employee Salary
, Youngest Child
, SMS Messages
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.
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.
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
The proper implementation and use of indexes are important for improving the performance of database queries.
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
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.
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
A programmer should use a language as a tool, always taking advantage of language-specific data types and built-in functions.
In mathematics, a union typically involves testing if an element exists in two or more sets. This definition also applies as an operator and function in various programming languages. As one of the most common collection operations, alongside intersection, it's an important topic for any candidate to understand.
Oracle PL/SQL is Oracles extension for SQL and Oracle relational database. Oracle PL/SQL adds support for procedural language features such as control statements, loops and classes. This allows the developer to further optimize and refine queries at the database, rather than application layer.
Bind variables can be used as a placeholder in an SQL query that can be replaced by input parameters as runtime. Because they allow more secure and faster query processing, bind variables are important for all SQL developers to understand.
A set is a collection of distinct objects. It's one of the most used types of collection, alongside arrays, lists, and maps. There are many different types of set, each with multiple specific optimizations and use cases. It is, therefore, one of the most important collections for a developer to be familiar with.
Exceptions exist in most modern programming languages, making it important for a programmer to understand them and know how to handle them.
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.
A transaction contains a set of modifications to be made to a database. A transaction can be committed to make its modifications to a database permanent, or rolled back to cancel any changes. Transactions are an important part of ensuring modifications made to a database are treated in a coherent, reliable, and error-free way.
A built-in function is a function provided by a language or framework that is included by default. It's important for candidates to know and use built-in functions, as they usually cover regularly used functionality reliably.
A table stores data as rows and columns. From databases to HTML layouts, as a data structure they are ubiquitous. They are an important structure for developers to understand and know how to use.
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.
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.
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
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.
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.
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.
A collection is a grouping of a variable number of data items. Many programming languages implement support for custom collections in their class libraries or utilities, as such it's an important topic for a developer to be familiar with.
Database cursors are a control structure for traversing over the records in a database. As they are often used when writing stored procedures, it's important for database admins and developers to be familiar with how and when to use them.