SQL, or Structured Query Language, is a standard programming language used to manage and manipulate data in relational databases. It is a powerful tool for data analysis, retrieval, and manipulation. In this article, we will cover the basics of SQL and give you a foundation to begin working with databases.
SQL Statements
SQL is made up of various statements, each serving a specific purpose. Here are some of the most commonly used SQL statements:
- SELECT – Retrieves data from a database
- INSERT – Inserts new data into a database
- UPDATE – Updates existing data in a database
- DELETE – Deletes data from a database
- CREATE – Creates a new table or database
- DROP – Deletes a table or database
SELECT Statement
The SELECT statement is used to query data from a database. It allows you to specify which columns you want to retrieve, as well as any conditions for filtering the data.
Syntax: SELECT column1, column2,… FROM table_name WHERE condition;
SELECT first_name, last_name FROM employees WHERE age > 30;
This query retrieves the first name and last name of all employees over the age of 30.
INSERT Statement
The INSERT statement is used to add new records to a table.
Syntax: INSERT INTO table_name (column1, column2,…) VALUES (value1, value2,…);
INSERT INTO employees (first_name, last_name, age) VALUES ('John', 'Doe', 28);
This query adds a new employee named Mitch Carter, aged 28, to the employees table.
UPDATE Statement
The UPDATE statement is used to modify existing records in a table.
Syntax: UPDATE table_name SET column1 = value1, column2 = value2,… WHERE condition;
UPDATE employees SET age = 29 WHERE first_name = 'John' AND last_name = 'Doe';
This query updates the age of the employee named Mitch Carter to 29.
DELETE Statement
The DELETE statement is used to remove records from a table.
Syntax: DELETE FROM table_name WHERE condition;
DELETE FROM employees WHERE first_name = 'John' AND last_name = 'Doe';
This query deletes the record of the employee named Mitch Carter from the employees table.
CREATE TABLE Statement
The CREATE TABLE statement is used to create a new table in a database.
Syntax: CREATE TABLE table_name (column1 datatype, column2 datatype,…);
CREATE TABLE departments (department_id INT PRIMARY KEY, department_name VARCHAR(50));
This query creates a new table called departments with two columns: department_id and department_name.
DROP TABLE Statement
The DROP TABLE statement is used to delete an entire table from a database.
Syntax: DROP TABLE table_name;
DROP TABLE departments;
This query deletes the departments table from the database.
In conclusion, learning the basics of SQL opens up many opportunities for working with and analyzing data. Understanding how to use SQL statements like SELECT, INSERT, UPDATE, DELETE, CREATE TABLE, and DROP TABLE is the first step towards becoming proficient in SQL. With some practice, you’ll be writing complex queries in no time!
Source: https://www.plcourses.com/introduction-to-sql-basics/
