- What is the difference between SQL and MySQL?
- What do you mean by DBMS? What are its different types?
- What are the types of joins in SQL? Give an example for each one.
- What is a Primary key?
- What are the different operators available in SQL?
- What is the need for group functions in SQL?
- What is a Relationship and what are they?
Please discuss these questions with your partners and post your answers as a comment on this gist when you are finished.
Team (Phamela, Ntokozo, Nhlanhla)
Answers.
SQL (Structured Query Language) is a standardized language used for managing and manipulating relational databases. MySQL, on the other hand, is a specific relational database management system (RDBMS) that uses SQL to perform database operations. In short, SQL is the language, while MySQL is a database software that uses SQL.
A DBMS (Database Management System) is software that interacts with end users, applications,
and the database itself to capture and analyze data.
Different types of DBMS include:
Relational DBMS (RDBMS): Organizes data into tables with rows and columns (e.g., MySQL, PostgreSQL).
NoSQL DBMS: Handles unstructured data and supports a variety of data models (e.g., MongoDB, Cassandra).
In-Memory DBMS: Stores data primarily in memory for faster access (e.g., Redis, SAP HANA).
Hierarchical DBMS: Organizes data in a tree-like structure (e.g., IBM's IMS).
Network DBMS: Uses a graph structure to represent relationships (e.g., CODASYL DBMS).
INNER JOIN: Returns records with matching values in both tables.
Example:
SELECT * FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
LEFT JOIN (or LEFT OUTER JOIN): Returns all records from the left table and matched records from the right table. Unmatched records from the right table will be null.
Example:
SELECT * FROM Orders
LEFT JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
RIGHT JOIN (or RIGHT OUTER JOIN): Returns all records from the right table and matched records from the left table. Unmatched records from the left table will be null.
Example:
SELECT * FROM Orders
RIGHT JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
FULL JOIN (or FULL OUTER JOIN): Returns all records when there is a match in either left or right table. Unmatched records from both tables will be null.
Example:
SELECT * FROM Orders
FULL OUTER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
CROSS JOIN: Returns the Cartesian product of both tables.
Example:
SELECT * FROM Orders
CROSS JOIN Customers;
SELF JOIN: Joins a table with itself.
Example:
SELECT A., B.
FROM Employees A, Employees B
WHERE A.ManagerID = B.EmployeeID;
A primary key is a column or a set of columns in a relational database table that uniquely identifies each row in that table. Here are the key characteristics and purposes of a primary key
Arithmetic Operators:
These are used to perform mathematical operations.
/ : Division
% : Modulus (remainder)
These are used to compare two values.
= : Equal to
<> or != : Not equal to
Performing Calculations on Groups: They enable calculations on subsets or groups of data, which is particularly useful in reporting and data analysis. For instance, calculating the average sales per department or total sales per month.
Efficiency: Group functions can process and summarize data efficiently, reducing the amount of data that needs to be processed and returned.
Data Analysis and Reporting: They are critical for data analysis and generating meaningful reports. Aggregating data helps in deriving insights and making informed business decisions.
6.a relationship refers to the connection or association between two or more tables. Relationships are essential for organizing data in a relational database, allowing the database to efficiently store, retrieve, and manage data.