What does `decimal(5,2)` mean in database design regarding precision and scale?

Understanding Precision and Scale in Decimal Data Types

In database design, specifying numerical data types often involves understanding the concepts of precision and scale. A recent inquiry arose regarding the interpretation of a "decimal(5,2)" column in a database, highlighting the significance of these parameters.

Precision: Counting the Digits

Precision refers to the maximum allowable number of digits in a numeric value, considering both integer and fractional parts. For example, a precision of 9 indicates that the number can have up to nine digits total.

Scale: Defining the Decimal Places

Scale, on the other hand, determines the maximum number of decimal places permitted. A scale of 2, for instance, allows for two fractional digits. This implies that the value can have a fractional part of the form 0.xx.

Interpreting decimal(5,2)

Applying these concepts to the example, decimal(5,2) signifies that the column can store numbers with a maximum of five digits (including both the integer and decimal parts) and two decimal places. Hence, a valid value would be 123.45, with a precision of 5 and a scale of 2.

Implications for Data Integrity

Understanding precision and scale is critical for ensuring data integrity. By defining these parameters, you limit the range of values that can be stored in the column, reducing the risk of data entry errors or out-of-range calculations.

Finding Documentation Online

While it may be challenging to locate comprehensive documentation on precision and scale online, consulting official database documentation or reputable technical forums (such as Stack Overflow) can provide valuable insights. These resources often contain detailed explanations and examples to clarify the topic.

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