Working with Dates and Times in SQL Server

When working with dates and times in SQL Server, it’s essential to understand how to correctly store and manipulate these values. In this tutorial, we’ll cover the basics of date and time data types, formats, and conversions.

Date and Time Data Types

SQL Server provides several data types for storing dates and times, including:

• DATETIME: This is the most commonly used data type for storing dates and times. It has a range of January 1, 1753, to December 31, 9999.
• DATETIME2: Introduced in SQL Server 2008, this data type provides a larger range (January 1, 0001, to December 31, 9999) and more precise time storage.

Date and Time Formats

When inserting or converting date and time values, it’s crucial to use the correct format. SQL Server supports several formats, including:

• YYYY-MM-DD HH:MM:SS: This is a common format for dates and times.
• YYYYMMDDTHH:MM:SS: This is an ISO-8601 compliant format that includes a ‘T’ separator between the date and time portions.
• ODBC formats, such as {ts'YYYY-MM-DD HH:MM:SS'} for timestamps.

Converting Date and Time Values

When converting date and time values from strings to SQL Server’s native data types, you can use the CONVERT function. For example:

SELECT CONVERT(datetime, '2022-07-25 14:30:00')

Alternatively, you can use the CAST function:

SELECT CAST('2022-07-25 14:30:00' AS datetime)

It’s essential to note that the conversion format depends on the SQL Server language and dateformat settings. To avoid issues, it’s recommended to use the ISO-8601 compliant format (YYYY-MM-DDTHH:MM:SS) or ODBC formats.

Best Practices

To avoid common pitfalls when working with dates and times in SQL Server:

• Use the DATETIME2 data type for more precise time storage and a larger range.
• Avoid using culture-specific date and time literals.
• Use ISO-8601 compliant formats or ODBC formats for conversions.
• Be aware of invalid dates (e.g., February 30) that can cause conversion errors.

Examples

Here are some examples of correct date and time conversions:

-- Using the ISO-8601 format
INSERT INTO table1 VALUES ('2022-07-25T14:30:00', '2022-01-01T00:00:00')

-- Using ODBC formats
INSERT INTO table1 VALUES ({ts'2022-07-25 14:30:00'}, {d'2022-01-01'})

-- Using the CONVERT function with the correct format
INSERT INTO table1 VALUES (CONVERT(datetime, '2022-07-25 14:30:00', 120), CONVERT(datetime, '2022-01-01 00:00:00', 120))

In conclusion, working with dates and times in SQL Server requires attention to data types, formats, and conversions. By following best practices and using the correct formats, you can avoid common errors and ensure accurate date and time storage and manipulation.