10. MySQL Part 1: Install, Create, Insert and SELECT

10.3 Creating Tables and Choosing Data Types

By Ravindra Bagale Last updated: 27 September 2026

Table mhanje rows aani columns. Column banavtana tyacha data type nit nivda – chukicha type mhanje chukicha data aani kadhi kadhi security problem.

Type	Stores	Example
`INT` / `BIGINT`	Whole numbers	`id`, `age`
`DECIMAL(10,2)`	Exact money values	`fees`
`VARCHAR(n)`	Text up to n characters	`name VARCHAR(100)`
`TEXT`	Long text	`caption`
`DATE` / `DATETIME` / `TIMESTAMP`	Dates and times	`joined_on DATE`
`BOOLEAN` (`TINYINT(1)`)	True/false	`is_active`
`ENUM('a','b')`	One of a fixed list	`mode ENUM('online','offline')`

USE cybercourse;
CREATE TABLE students (
  student_id INT AUTO_INCREMENT PRIMARY KEY,
  name       VARCHAR(100) NOT NULL,
  email      VARCHAR(150) UNIQUE,
  city       VARCHAR(50)  NOT NULL,
  age        INT,
  fees_paid  DECIMAL(10,2) DEFAULT 0,
  joined_on  DATE
);

CREATE TABLE courses (
  course_id   INT AUTO_INCREMENT PRIMARY KEY,
  course_name VARCHAR(100) NOT NULL,
  duration_wk INT
);

CREATE TABLE enrollments (
  enroll_id  INT AUTO_INCREMENT PRIMARY KEY,
  student_id INT,
  course_id  INT,
  score      INT,
  FOREIGN KEY (student_id) REFERENCES students(student_id),
  FOREIGN KEY (course_id)  REFERENCES courses(course_id)
);

SHOW TABLES;
DESCRIBE students;             -- or: DESC students;
SHOW CREATE TABLE students\G   -- full definition

Ravindra Bagale's Tip

Password sathi VARCHAR(20) column banavnare khup students aahet – mhanje te plain password thevnar! Password kadhi plain thevaycha nahi; PHP madhe password_hash() ne hash karun VARCHAR(255) madhe theva. Table design pasunach security suru hote.

Practice task

Create the three tables above and run DESCRIBE on each. Explain what AUTO_INCREMENT PRIMARY KEY and FOREIGN KEY do in your own words.