Timestamp vs. Datetime in SQL Server: When Should You Use Each?

Timestamp vs. Datetime in SQL Server: Unraveling the Differences

The concepts of Timestamp and Datetime in SQL Server may seem similar at first glance, but they play distinct roles in representing temporal data. Let's delve into their key differences to clarify the distinction:

Storage and Generation:

Timestamp is not a data type but rather a synonym for "rowversion." It automatically generates a unique binary value for each row upon insertion or update. This value serves as a unique identifier for the row and ensures the row's integrity. Datetime, on the other hand, is a regular data type used to store and manipulate dates and times. The values for Datetime columns can be specified manually or generated by SQL Server based on the rules defined for the column.

Data Range and Resolution:

Timestamp utilizes a 6-byte binary value with a resolution of approximately 100 nanoseconds to represent a point in time. Datetime, on the other hand, can store a wider range of dates and times in various formats, including date, time, and date and time combined. The precision of Datetime depends on the specific format used.

Automatic Generation:

The primary difference between Timestamp and Datetime lies in their automatic generation. Timestamp is automatically generated and maintained by SQL Server, making it suitable for scenarios where a unique identifier is required for each row. Datetime values can be manually specified or generated using functions, making them ideal for applications where data entry or calculations are involved.

Durability and Concurrency:

Timestamp values are durable, meaning they are preserved across transaction boundaries. They cannot be modified directly and are particularly useful for tracking row insertions, updates, and conflicts in concurrent environments. Datetime values, however, are not inherently durable and can be updated or modified by the application.

In summary, Timestamp is a unique identifier generated by SQL Server for row versioning, while Datetime is a regular data type used to store and manipulate dates and times. The choice between the two depends on the specific requirements of the application and whether automatic generation and uniqueness are necessary.

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