What is SQL?
SQL (Structured Query Language) is a standardized programming language used for managing and manipulating relational databases. It allows you to perform various operations like querying data, updating records, deleting data, and creating or altering database structures.
Basic SQL Syntax
Here are some fundamental SQL commands and their syntax:
SELECT
Used to retrieve data from a database.sqlSELECT column1, column2, ... FROM table_name;Example:
sqlSELECT first_name, last_name FROM employees;WHERE
Used to filter records.sqlSELECT column1, column2, ... FROM table_name WHERE condition;Example:
sqlSELECT first_name, last_name FROM employees WHERE department = 'Sales';INSERT INTO
Used to insert new records into a table.sqlINSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);Example:
sqlINSERT INTO employees (first_name, last_name, department) VALUES ('John', 'Doe', 'HR');UPDATE
Used to modify existing records.sqlUPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;Example:
sqlUPDATE employees SET department = 'Marketing' WHERE last_name = 'Doe';DELETE
Used to delete records.sqlDELETE FROM table_name WHERE condition;Example:
sqlDELETE FROM employees WHERE last_name = 'Doe';CREATE TABLE
Used to create a new table.sqlCREATE TABLE table_name ( column1 datatype, column2 datatype, ... );Example:
sqlCREATE TABLE employees ( id INT PRIMARY KEY, first_name VARCHAR(50), last_name VARCHAR(50), department VARCHAR(50) );ALTER TABLE
Used to modify the structure of an existing table.sqlALTER TABLE table_name ADD column_name datatype;Example:
sqlALTER TABLE employees ADD email VARCHAR(100);DROP TABLE
Used to delete a table and all of its data.sqlDROP TABLE table_name;Example:
sqlDROP TABLE employees;
Conclusion
SQL is essential for interacting with relational databases. By mastering these basic commands, you can perform most of the necessary database operations, from creating and managing tables to querying and updating data.
