Understanding Data Types

Definition

Data types in SQL are the classifications that specify the kind of data that can be stored in a database column. They play a crucial role in how the database manages data, influencing both the operations that can be performed on the data and how much storage space the data will consume. Choosing the correct data type for each column is essential for ensuring data integrity and optimizing performance.

Common Data Types

• Numeric Data Types:
  • INT: This data type is used for storing whole numbers without decimals. For example, you might use it for employee IDs or counts of items.
  • FLOAT: This type is used for storing numbers that require decimals. It’s useful for storing values like prices or measurements where precision is important.
• Character Data Types:
  • CHAR(n): This is a fixed-length string type. If you define a column as CHAR(5), it will always store five characters, padding with spaces if necessary. It is useful for storing fixed-length codes, like state abbreviations.
  • VARCHAR(n): This type is variable-length and can hold up to n characters. It is more flexible than CHAR and is commonly used for names or addresses where the length may vary.
• Date and Time Data Types:
  • DATE: This type stores dates in a year-month-day format. It is perfect for fields that track dates, such as a customer's registration date.
  • TIMESTAMP: This type stores both date and time, providing a complete picture of when an event occurred. It’s useful for tracking when records are created or modified.

Understanding these data types helps in designing the database effectively, allowing you to store and retrieve data accurately and efficiently.

Create, Update & Delete Operations

Definition

Create, Update, and Delete operations, often abbreviated as CRUD, are fundamental actions that allow users to interact with and manage data stored in a database. Each of these operations performs a specific function related to data management.

Create Operation

The Create operation is used to add new records to a table. This is done with the INSERT INTO statement, which specifies the table you want to add data to and the values for each column.

Example of Create

To add a new customer to a customers table, you would write:

INSERT INTO customers (customer_name, contact_email)
VALUES ('John Doe', '[email protected]');

In this example, a new row is created in the customers table with the name "John Doe" and the email "[email protected]."

Update Operation

The Update operation allows you to modify existing records. It is performed using the UPDATE statement, which specifies the table to be updated and the new values for one or more columns, along with a condition to identify which records to update.