A Complete Guide to the MySQL LPAD() Function

Learn how the LPAD() function works in MySQL, including syntax, usage, and examples.

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Introduction

When working with databases, formatting strings to meet specific requirements is a common task. MySQL’s LPAD() function is a handy tool for precisely this purpose—it lets you pad a string with additional characters on the left side until it reaches a desired length. Whether you’re standardizing ID formats, aligning text outputs, or preparing data for fixed-width systems, LPAD() ensures your strings are consistently structured.

In this guide, we’ll break down how LPAD() works, explore its syntax, and walk through practical examples to help you master its use in real-world scenarios.

What LPAD() Does

The LPAD() function takes a string and extends it to a specified length by adding padding characters to the left. If the original string is already longer than the target length, it gets truncated from the right.

The basic syntax is:

LPAD(string, length, pad_string)
  • string: The input text you want to pad.
  • length: The total number of characters the result should have.
  • pad_string: The characters used for padding (often a space, zero, or another symbol).

Basic Padding Examples

Padding with Spaces (Default Behavior)

If you don’t specify a padding character, LPAD() uses spaces by default:

SELECT LPAD('hello', 10) AS PaddedText;

Result:

     hello

(5 spaces + “hello” = 10 characters total)

Padding with Custom Characters

You can use any character (or even multiple characters) for padding. For example, padding a number with leading zeros:

SELECT LPAD('42', 5, '0') AS PaddedNumber;

Result:

00042

This is especially useful for formatting invoice numbers, product codes, or other identifiers.

Handling Truncation

If the original string is longer than the specified length, LPAD() cuts off the excess characters from the end:

SELECT LPAD('database', 4, '-') AS TruncatedText;

Result:

data

(Only the first 4 characters are kept.)

Real-World Use Cases

Formatting Employee IDs

Suppose you have a table of employees with IDs that must be 8 digits long, padded with zeros:

SELECT LPAD(employee_id, 8, '0') AS FormattedID
FROM employees;

Example Output:

00012345
00098765

Generating Fixed-Width Reports

When exporting data for legacy systems that require fixed-width columns, LPAD() ensures alignment:

SELECT
    LPAD(product_name, 20, ' ') AS Product,
    LPAD(price, 10, ' ') AS Price
FROM products;

This keeps all entries neatly aligned, even if their original lengths vary.

Combining LPAD() with Other Functions

You can chain LPAD() with functions like CONCAT() for dynamic formatting. For example, creating a standardized order reference:

SELECT
    CONCAT('ORD-', LPAD(order_id, 6, '0')) AS OrderRef
FROM orders;

Result:

ORD-000123
ORD-004567

Performance Notes

While LPAD() is efficient for small to medium datasets, excessive string manipulation in large-scale queries can impact performance. If you’re frequently padding the same column, consider storing the padded version in the database or using generated columns.

Conclusion

The LPAD() function is a versatile tool for string formatting in MySQL. Whether you’re aligning text, normalizing identifiers, or preparing data for export, it provides a simple way to ensure consistency. By mastering LPAD(), you’ll save time on manual formatting and keep your database outputs clean and professional.

Next time you need to enforce a specific text structure, remember: LPAD() has you covered!