When working with SQL Server, there may be times when you need to convert a column or variable from one data type to another. This is often necessary when you want to compare values of different data types or when you need to format the output in a specific way. In SQL Server, you have two options for performing these conversions: CAST and CONVERT.

CAST is a commonly used function for data type conversion. It is often preferred by developers due to its familiarity, especially for those who have experience with programming languages like C++ or C#. The syntax for using CAST is straightforward:

SELECT CAST(column_name AS new_data_type)
FROM table_name;

On the other hand, CONVERT is another function available in SQL Server for data type conversion. It offers additional flexibility by allowing you to specify a formatting style when converting certain data types like dates, money, float, or real values to a varchar. The syntax for using CONVERT is as follows:

SELECT CONVERT(new_data_type, column_name, style)
FROM table_name;

One advantage of CONVERT over CAST is the ability to format the output according to specific styles. For example, if you want to convert a date to a varchar and display it in the format “MM/DD/YYYY”, you can use the following code:

SELECT CONVERT(varchar, GETDATE(), 101);

This will return the current date in the format “01/23/2006”. Similarly, you can use different styles to achieve different date formats. For instance, the style “103” will display the date in the format “DD/MM/YYYY”.

Another useful feature of CONVERT is its ability to format money values. By specifying the appropriate style, you can control the display of decimal places and thousands separators. For example:

DECLARE @amount MONEY
SET @amount = 1000000

SELECT CONVERT(varchar, @amount, 1);

This will format the money value as “1,000,000.00”.

It’s important to note that both CAST and CONVERT have their own advantages and use cases. If you simply need to convert a value without any specific formatting requirements, either function can be used interchangeably. However, if you need to format the output in a specific way, CONVERT provides more flexibility with its style parameter.

In conclusion, understanding the differences between CAST and CONVERT in SQL Server can help you effectively manipulate and format data. Whether you prefer the simplicity of CAST or the flexibility of CONVERT, both functions are valuable tools in your SQL Server arsenal.