, Insert Employee
, Query Performance
, Lap Times
, Remove Element
, User Statistics
, Merge Lists
, Employee Salary
, ATM Locations
, Ban Users
, Bank Branches
, Cheapest Product
, Employee Manager
, Hospital Patients
, Index Performance
, Menu Items
, Merge Stock Index
, Movies Live
, Restaurant Menu
, SMS Messages
, Student Activities
, Youngest Child
, Manager Sales
, Delete Orders
, Average Salary
, Movie Genres
, Auto Show
, Department Report
, Student Rankings
, Welfare Organization
, Student Max Score
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.
Exceptions exist in most modern programming languages, making it important for a programmer to understand them and know how to handle them.
The proper implementation and use of indexes are important for improving the performance of database 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.
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.
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.
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.
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
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.
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.
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.
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.
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.
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 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.
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
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.
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
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.
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.
The CASE statement is SQL's control statement. It goes through conditions and returns a value.