Oracle database fundamentals - SQL queries

What is SQL?

• SQL is a programming language used for creating websites.

• SQL is a software for graphic design.

• SQL is a type of computer hardware.

• SQL is a domain-specific language used for managing data in relational database management systems.

What is the difference between SQL and PL/SQL?

• SQL is a programming language, while PL/SQL is a markup language.

• SQL is used for front-end development, while PL/SQL is used for back-end development.

• SQL is a standard language for managing relational databases, while PL/SQL is Oracle's proprietary extension of SQL that adds procedural capabilities.

• SQL and PL/SQL are interchangeable terms.

Explain the SELECT statement in SQL.

• The SELECT statement in SQL is used to delete data from a database.

• The SELECT statement in SQL is used to update data in a database.

• The SELECT statement in SQL is used to retrieve data from a database.

• The SELECT statement in SQL is used to create a new database.

What is the purpose of the WHERE clause in SQL?

• To filter records based on a specified condition.

• To sort records in ascending order

• To create new tables

• To update existing records

How do you use the GROUP BY clause in SQL?

• SELECT * FROM table_name GROUP BY column_name;

• SELECT column_name, aggregate_function(column_name) FROM table_name GROUP BY column_name;

• SELECT column_name FROM table_name GROUP BY column_name;

• SELECT column_name, aggregate_function(column_name) FROM table_name ORDER BY column_name;

What is the difference between INNER JOIN and OUTER JOIN?

• INNER JOIN combines rows from both tables based on a specified condition, while OUTER JOIN combines all rows from both tables.

• INNER JOIN only includes rows with NULL values, while OUTER JOIN excludes rows with NULL values.

• INNER JOIN is used to combine rows from two tables based on a related column, while OUTER JOIN is used to combine rows from two tables without a related column.

• INNER JOIN selects rows with matching values in both tables, while OUTER JOIN selects all rows from both tables.

Explain the concept of subqueries in SQL.

• Subqueries in SQL are used to update data directly in the database

• Subqueries in SQL can only be used in SELECT statements

• Subqueries in SQL always return a single value

• Subqueries in SQL are queries nested within another query. They can be used to retrieve data that will be used in the main query, allowing for more complex and specific data retrieval operations.

How do you perform data manipulation using SQL?

• Use Python programming language for data manipulation

• Perform data manipulation using HTML and CSS

• Manipulate data in a database using Microsoft Excel

• Use SQL commands such as SELECT, INSERT, UPDATE, DELETE, and JOIN to manipulate data in a database.

What are the different types of SQL constraints?

• INDEX

• DEFAULT

• NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK

• CONSTRAINT

• SPECIAL

Explain the concept of indexing in SQL.

• Indexing in SQL is a technique to delete data from tables

• Indexing in SQL is used to sort data alphabetically

• Indexing in SQL is a method to encrypt data in tables

• Indexing in SQL is a technique used to improve query performance by creating data structures on columns in tables for faster data retrieval.