DateTime vs DateTime2 in SQL Server

DateTime vs DateTime2 in SQL Server

Introduction:
When working with SQL Server, developers often encounter two similar data types for storing date and time information: DateTime and DateTime2. While they serve the same purpose, there are some important differences between the two that users should be aware of to make informed decisions about which one to use in their database schema.

1. DateTime:
The DateTime data type in SQL Server is used to store both date and time values with a precision of approximately 3.33 milliseconds. It has a range from January 1, 1753, to December 31, 9999. The DateTime type uses 8 bytes of storage.

Example:

sql
CREATE TABLE ExampleTable1 (
    ID INT PRIMARY KEY,
    EventDateTime DateTime
);

INSERT INTO ExampleTable1 (ID, EventDateTime)
VALUES (1, '2023-07-23 12:34:56');

Explanation:
In this example, we create a table ExampleTable1 with a column named EventDateTime of type DateTime. We then insert a record with ID 1 and a specific date and time value into the table.

2. DateTime2:
The DateTime2 data type was introduced in SQL Server 2008. It is an extension of the DateTime type and offers higher precision for storing date and time values. The DateTime2 type can store values with a fractional second precision of up to 7 digits, providing more accurate results. It has a broader range, starting from January 1, 0001, to December 31, 9999. The DateTime2 type uses between 6 to 8 bytes of storage depending on the precision.

Example:

sql
CREATE TABLE ExampleTable2 (
    ID INT PRIMARY KEY,
    EventDateTime2 DateTime2(3) -- 3-digit fractional seconds precision
);

INSERT INTO ExampleTable2 (ID, EventDateTime2)
VALUES (1, '2023-07-23 12:34:56.789');

Explanation:
In this example, we create a table ExampleTable2 with a column named EventDateTime2 of type DateTime2(3). The (3) specifies that we want to store fractional seconds with a precision of 3 digits. We then insert a record with ID 1 and a specific date and time value with fractional seconds into the table.

Comparison and Recommendations:

• Use DateTime when you need to store date and time values with a precision of around 3 milliseconds and a range from 1753 to 9999. It's suitable for most general-purpose scenarios.
• Use DateTime2 when you require higher precision for storing date and time values with fractional seconds. It is especially useful for scenarios where you need more accurate time measurements or need to store dates far in the past or future.
• DateTime2 is generally the preferred choice due to its wider range, higher precision, and compatibility with modern applications.

Conclusion:
Both DateTime and DateTime2 are valuable data types in SQL Server, but the choice depends on the specific requirements of your application. Consider the range, precision, and compatibility needs before selecting the appropriate data type for your date and time storage.