MySQL provides the CAST and CONVERT functions to perform explicit type conversions, allowing you to convert data from one data type to another. Both functions essentially serve the same purpose, but there are some differences in their syntax and usage.
CAST function
The CAST() function is used to explicitly convert an expression or a value from one data type to another. The syntax for the CAST() function is as follows:
CAST(expression AS data_type)
Here, expression is the value or expression you want to convert, and data_type is the target data type you want to convert the expression to.
Example:
SELECT CAST('123' AS SIGNED) AS converted_value;
In this example, the string ‘123’ is cast as a signed integer, resulting in the converted value 123.
CONVERT function
The CONVERT() function is another way to achieve the same result as CAST(). The syntax for the CONVERT() function is slightly different:
CONVERT(expression, data_type)
Here, expression is the value or expression to be converted, and data_type is the target data type.
Example:
SELECT CONVERT('456', SIGNED) AS converted_value;
This example converts the string ‘456’ to a signed integer using the CONVERT() function.
Key Points
Data Type Compatibility: Both CAST() and CONVERT() functions support various data types, and the success of the conversion depends on the compatibility of the source and target data types.
Common Use Cases: Converting strings to numbers or vice versa. Changing the data type of a column temporarily for specific queries.
Error Handling: If the conversion is not possible, MySQL may return a NULL value or generate an error. It’s essential to ensure that the source and target data types are compatible.
Conclusion
The CAST and CONVERT functions in MySQL are valuable tools when you need to explicitly convert data types in your queries. Whether you choose CAST() or CONVERT() depends on your preference and the specific requirements of your query. These functions are particularly useful when dealing with mixed data types or when you need to standardize the type of data for further processing or comparisons in your SQL statements.