SQL LEFT JOIN – Explained with Syntax and Real-Life Examples

Introduction

In SQL, text data types are used to store alphanumeric values like names, addresses, emails, and descriptions. Choosing the correct text type — CHAR, VARCHAR, or TEXT — is important for optimizing storage space, query speed, and database performance.

In this section, you'll learn the definitions, differences, and best use cases for each text data type.

1. CHAR (Fixed-Length String)

CHAR is used to store fixed-length strings. If the stored string is shorter than the defined length, SQL automatically pads it with spaces to match the specified size.

Features:

• Fixed length
• Fast and predictable performance
• Uses extra storage if the data is often shorter than the specified length

Syntax:

column_name CHAR(length);

length = number of characters (1 to 255 depending on the database system)

Example:

CREATE TABLE countries (
        country_code CHAR(2),
        country_name CHAR(50)
            );

country_code like 'US', 'IN', 'UK' will always take 2 characters.

When to Use CHAR:

• Data with a constant size, such as country codes, gender ('M', 'F'), state abbreviations
• Fixed-format fields like credit card types ('VISA', 'MC')
• When exact storage size is known and consistent

2. VARCHAR (Variable-Length String)

VARCHAR stands for Variable Character. It stores variable-length strings, meaning only the actual characters are stored without unnecessary padding.

Features:

• Variable length
• More space-efficient than CHAR for varying-length text
• Slightly slower than CHAR when processing large volumes (because of extra calculations for string lengths)

Syntax:

column_name VARCHAR(length);

length = maximum number of characters allowed

Example:

CREATE TABLE employees (
        first_name VARCHAR(50),
        email VARCHAR(100)
            );

Names and emails can vary in length, making VARCHAR ideal.

When to Use VARCHAR:

• Data with unpredictable or variable length
• Names, emails, addresses, and descriptions under 255-65535 characters
• Most general-purpose text fields

3. TEXT (Large Text Field)

TEXT is used to store large amounts of text like long descriptions, blog posts, comments, or articles.

Features:

• Meant for large text storage (up to 65,535 characters for standard TEXT in MySQL)
• Cannot have a default value (in some databases like MySQL)
• TEXT fields are stored outside the main table with a pointer reference
• Different variants exist (TINYTEXT, MEDIUMTEXT, LONGTEXT) for various sizes

Syntax:

column_name TEXT;

Example:

CREATE TABLE articles (
        id INT,
        title VARCHAR(255),
        body TEXT
           );

body will store the full article content, which can be very large.

When to Use TEXT:

• Long-form text fields (comments, articles, reviews, reports)
• Data that exceeds normal VARCHAR limits
• When exact storage requirements are unknown or potentially very large

Quick Comparison: CHAR vs VARCHAR vs TEXT

Important Tips

• Use CHAR only when all values will be exactly the same length
• VARCHAR is the best choice for most standard text fields
• Reserve TEXT for content that exceeds VARCHAR limits
• Consider VARCHAR(MAX) in SQL Server for large text that might need indexing
• Be aware that TEXT fields may have limitations on default values and full-text indexing

What is a LEFT JOIN in SQL?

A LEFT JOIN (also called a LEFT OUTER JOIN) returns all records from the left table, and the matched records from the right table. If there's no match in the right table, it returns NULL for those columns.

Think of it as: "Give me everything from the left table, and matching info from the right table — if available."

LEFT JOIN Syntax

SELECT table1.column1, table2.column2, ...
        FROM table1
        LEFT JOIN table2
        ON table1.common_column = table2.common_column;

table1 is the left table

table2 is the right table

common_column is used to match rows between them

Real-Life Example

Tables:

customers

orders

Query:

SELECT 
          customers.name, 
          orders.order_date
        FROM customers
        LEFT JOIN orders
        ON customers.id = orders.customer_id;

Result:

Charlie appears even without an order — that's what LEFT JOIN does.

Use Cases for LEFT JOIN

• Find users who haven't placed any orders
• Display all products, even those with no sales
• Create summary reports that include everything, even missing data

LEFT JOIN vs INNER JOIN

LEFT JOIN with Aliases

SELECT c.name, o.order_date
        FROM customers c
        LEFT JOIN orders o
        ON c.id = o.customer_id;

Shorter and cleaner for complex queries.

Conclusion

Use LEFT JOIN when you want to:

• Keep all records from one table
• Include related data from another table
• Still show results even when there's no match