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:
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 tableyour_table
. This will return a new column nameddate_without_time
containing only the date portion.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
orCONVERT
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;
Using the DATEADD Function (Limited Use Case):
- It involves unnecessary calculations.
- It might be less intuitive for others reading your code.
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
orCONVERT
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.
sql-server datetime date-conversion