What Are SQL Data Types?

When you use a database, you are really organizing and storing information in a structured way. To do this effectively, SQL databases use data types, which act like containers designed to hold specific kinds of information. Imagine trying to put soup in a basket or sand in a bottle—each container is suited to a certain kind of content. In the same way, SQL data types make sure each piece of data goes into the right kind of "container," ensuring accuracy, efficiency, and reliability in your database.

CREATE TABLE sample_intro (
    id INTEGER PRIMARY KEY,
    name VARCHAR(50),
    birth_date DATE,
    is_active BOOLEAN
);

In the sample_intro table you just saw, each column is defined with a specific data type:

• The id column uses the INTEGER type, which means it can only store whole numbers. This is perfect for unique identifiers, like user IDs;
• The name column uses VARCHAR(50), allowing you to store up to 50 characters of text—ideal for names or short descriptions;
• The birth_date column uses the DATE type, which is designed to hold calendar dates, making it easy to sort or filter by birthdays;
• The is_active column uses the BOOLEAN type, which can only be TRUE or FALSE, representing simple yes/no or on/off values.

By specifying these data types, you help the database understand how to store, validate, and process each piece of information. This prevents mistakes, like accidentally putting text where a number should be, and makes your data more reliable.

INSERT INTO sample_intro (id, name, birth_date, is_active) VALUES
(1, 'Alice', '1990-05-15', TRUE),
(2, 'Bob', '1985-11-23', FALSE),
(3, 'Charlie', '2000-01-01', TRUE),
(4, 'Diana', NULL, FALSE);