When working with numerical data in a database, one of the most common data types used is the decimal data type. This data type allows for precise storage and manipulation of decimal numbers, making it a popular choice for financial and scientific data. However, there may be instances where the default precision of a decimal column in Microsoft SQL Server is not enough. In this article, we will explore how to alter the precision of a decimal column in Microsoft SQL Server.

Before we dive into the technical aspects of altering precision, let us first understand what precision means in the context of a decimal data type. Precision refers to the total number of digits that can be stored in a decimal column, including both the digits before and after the decimal point. For example, a decimal column with a precision of 5 can store numbers up to 99.999. This means that precision plays a crucial role in determining the accuracy of the data stored in a decimal column.

To alter the precision of a decimal column, we need to use the ALTER TABLE statement. This statement allows us to modify the structure of an existing table in the database. The syntax for altering the precision of a decimal column is as follows:

## ALTER TABLE table_name

## ALTER COLUMN column_name decimal(precision, scale)

Let us break down this statement. The first line specifies the table name that we want to alter. The second line specifies the column name that we want to modify. In our case, it would be the decimal column whose precision we want to change. The third line defines the data type of the column, which is decimal, followed by the new precision and scale values inside the parentheses.

Now, you may be wondering what scale refers to in this context. Scale refers to the number of digits that can be stored after the decimal point. For example, a scale of 2 would allow for two digits after the decimal point, while a scale of 0 would not allow any digits after the decimal point. It is important to note that the scale cannot be greater than the precision value.

Let us look at an example to better understand how to alter the precision of a decimal column. Suppose we have a table named Sales with a column named Price, which is currently defined as decimal(10,2). This means that the Price column can store a maximum of 10 digits, with 2 of them after the decimal point. However, let us say that we want to increase the precision to 12 and scale to 4. To do so, we would use the following statement:

## ALTER TABLE Sales

## ALTER COLUMN Price decimal(12,4)

This statement would alter the precision and scale of the Price column, allowing for more accurate storage of decimal numbers.

It is important to note that altering the precision of a decimal column can have implications on the existing data. For example, if the new precision is smaller than the existing precision, data loss may occur. Similarly, if the new precision is larger than the existing precision, the data will need to be rounded, leading to potential inaccuracies. Therefore, it is crucial to carefully consider the impact of altering the precision before making any changes.

In conclusion, altering the precision of a decimal column in Microsoft SQL Server is a relatively straightforward process. By using the ALTER TABLE statement and specifying the desired precision and scale values, we can modify the structure of an existing table to suit our needs. However, it is essential to carefully consider the implications of altering precision, as it can have a significant impact on the accuracy of the data stored in the column. With this knowledge, you can now confidently work with decimal data types in Microsoft SQL Server and make necessary changes to suit your data requirements.