Understanding and Proper Usage of timestamp Data Type in SQL Server

Fundamental Characteristics of timestamp Data Type

In SQL Server database systems, the timestamp data type is often misunderstood as a time stamp, but it actually represents an automatically generated binary version-stamping mechanism. According to Microsoft official documentation, timestamp exposes automatically generated, unique binary numbers within a database, primarily used for version-stamping table rows. With a storage size of 8 bytes, it is essentially an incrementing number sequence that does not preserve any date or time information.

Root Cause of Explicit Insertion Failure

When attempting to execute the following SQL statement:

create table demo (
    ts timestamp
)

insert into demo select current_timestamp

The system throws an error: "Cannot insert an explicit value into a timestamp column. Use INSERT with a column list to exclude the timestamp column, or insert a DEFAULT into the timestamp column." This occurs because timestamp column values are entirely managed by SQL Server automatically, prohibiting users from explicitly specifying or modifying them.

Correct DateTime Storage Solutions

To store actual date and time information, dedicated datetime data types should be used. Below is the recommended implementation:

create table demo (
    ts datetime
)

insert into demo select current_timestamp

select ts from demo

The execution returns formatted datetime values, such as: "2014-04-04 09:20:01.153". This approach accurately records time information, fully meeting business requirements.

Appropriate Use Cases for timestamp

timestamp is designed for optimistic concurrency control, detecting row modifications through automatically updated binary values. A typical usage pattern is:

create table products (
    id int primary key,
    name varchar(50),
    price decimal(10,2),
    version timestamp
)

insert into products (id, name, price) values (1, 'Product A', 19.99)

Record the timestamp value when reading data, and verify it remains unchanged during updates to prevent concurrency conflicts.

Alternative Approaches and Considerations

In newer SQL Server versions, timestamp has been renamed to rowversion to better reflect its functionality. If copying timestamp values is necessary, the target column type can be changed to binary(8) or varbinary(8), though this sacrifices the original version control capabilities.

For time storage, besides datetime, options like smalldatetime, date, time, or datetime2 can be selected based on precision requirements, each offering distinct characteristics in storage range and accuracy.