Keeping it Simple: Removing Time Portions from Datetime Values in SQL Server

• Datetime: This datatype stores both the date and time information in a single field.
• Date: This datatype only stores the date portion, excluding the time.

Removing the Time Portion:

There are two main methods to remove the time portion from a datetime value in SQL Server:

1. CAST to Date Datatype:

   The CAST function allows you to convert a value from one data type to another. In this case, you'll convert the datetime value to a date type. Here's the syntax:

   SELECT CAST(your_datetime_field AS date) AS date_without_time
   FROM your_table;
   

   Replace your_datetime_field with the actual name of your datetime column in the table your_table. This will return a new column named date_without_time containing only the date portion.

2. CONVERT Function with Style Code:

   The CONVERT function offers more flexibility for data type conversions. You can use it with a specific style code to achieve the date conversion. Here's the syntax:

   SELECT CONVERT(date, your_datetime_field) AS date_without_time
   FROM your_table;
   

   This achieves the same result as the CAST method.

Choosing the Right Method:

Both methods are valid and achieve the same outcome. Here's a tip for choosing:

• If you're permanently storing the date-only version of the data, consider using the date datatype for the new column.
• If you only need the date portion for temporary calculations or display purposes within your query, CAST or CONVERT might be preferable.

Additional Notes:

• These methods assume your datetime field doesn't contain any null values. If it does, you might need to handle nulls appropriately in your query.
• For better performance, consider using the date datatype if you know you'll primarily work with just the date portion.

-- Assuming you have a table 'Sales' with a datetime column 'SaleDate'
SELECT CAST(SaleDate AS date) AS DateOfSale
FROM Sales;

This code retrieves the SaleDate (datetime) from the Sales table and converts it to a date using CAST. The result is stored in a new column named DateOfSale.

Example 2: Using CONVERT with Style Code

-- Assuming you have a table 'Customers' with a datetime column 'JoinedOn'
SELECT CONVERT(date, JoinedOn) AS JoinedDate
FROM Customers;

1. Using the DATEADD Function (Limited Use Case):

   • It involves unnecessary calculations.
   • It might be less intuitive for others reading your code.

2. Storing Dates as the DATE Datatype:

• If you need to occasionally extract the date portion from existing datetime data for calculations or display purposes within a query, then CAST or CONVERT are the best options.
• If you're working with new data where you know you'll only need the date information, using the date datatype for storage is the most efficient approach.
• Avoid using DATEADD for time removal as it's less performant and less readable.