How to Use MySQL Cast to Convert Data to VARCHAR

Casting data types in MySQL is a great way to convert values from one data type to another, especially when you need to treat data types like integers, dates, or others as strings. This technique is particularly useful for concatenating numbers with strings, formatting dates in a specific way, or ensuring database inputs are uniform.

In this article, we'll delve into the practical applications and intricacies of casting data types in MySQL, unlocking its power for string manipulation, formatting, and data uniformity.

What are cast and convert in MySQL?

MySQL offers two primary functions for data type conversion: CAST and CONVERT. These functions are your go-to solutions for converting values to VARCHAR, each with its own syntax and use cases.

How to use cast in MySQL?

The CAST function enables you to transform a value into a specified type efficiently. Here's how to cast a value to VARCHAR:

CAST(value AS VARCHAR(length))

In this syntax, value represents the data you wish to cast, and length specifies the string's desired length. For example:

SELECT CAST(12345 AS VARCHAR(20));

This query transforms the integer 12345 into a string value "12345".

How to use convert in MySQL?

Similarly, CONVERT allows for type conversion with a slightly different syntax, providing additional flexibility for character set conversions. To convert a value to VARCHAR with CONVERT, use the following syntax:

CONVERT(value, VARCHAR(length))

Or, for converting with a specific character set:

CONVERT(value USING charset)

For instance, converting an integer to a string with CONVERT looks like this:

SELECT CONVERT(12345, VARCHAR(20));

Examples

Casting to VARCHAR proves invaluable in scenarios requiring string format for operations like concatenation or applying string functions to numeric or date fields.

Concatenating strings with numbers

To seamlessly concatenate numbers with strings, casting the number to a VARCHAR prevents type errors:

SELECT CONCAT('Order Number: ', CAST(order_id AS VARCHAR(10))) AS order_string
FROM orders;

Formatting dates

For custom date formatting, first cast the date to a VARCHAR then apply string functions:

SELECT CONCAT(DAY(CAST(order_date AS VARCHAR(10))), '/', MONTH(CAST(order_date AS VARCHAR(10))), '/', YEAR(CAST(order_date AS VARCHAR(10)))) AS formatted_date
FROM orders;

Conclusion

Casting to VARCHAR in MySQL simplifies data manipulation, enabling smooth conversions and operations across various data types. By using CAST and CONVERT functions, you leverage MySQL's capabilities to format data for display, combine text with numerical or date values, and maintain data type consistency across your SQL queries.