Скачать или смотреть How to Combine Date and Time Columns into a Single DateTime Column in SQL

Learn how to efficiently combine separate `Date` and `Time` columns into a single `DateTime` column in SQL Server. This step-by-step guide provides you with a clear solution and optimization tips.
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How to Combine Date and Time Columns into a Single DateTime Column in SQL

In SQL databases, it's common to store date and time values in separate columns. However, there are times when you may want to combine these two columns into a single DateTime column. This is particularly useful for data consolidation and when you want to enhance the efficiency of your data queries. In this post, we will walk you through the process of combining two datetime2 columns—namely Date and Time—into a single column called OrderDate in a SQL Server database.

The Problem

You have two separate columns in your database: one for date (Date) and another for time (Time). You need to combine these two into a single datetime2 column for better data handling. After the combination, you will also want to remove the old columns.

Here’s a quick recap of what you will accomplish:

Combine the Date and Time columns

Update the existing column OrderDate

Remove the obsolete columns afterward

The Solution

Step 1: Combining Date and Time

To combine the Date and Time columns, you can use the following SQL query which utilizes the DATEADD and DATEDIFF functions.

Here is how it looks:

[[See Video to Reveal this Text or Code Snippet]]

Breaking Down the Query

DATEDIFF(day, 0, Date): This part calculates the difference in days from an anchor date (0, which represents the base date '1900-01-01') to your Date.

DATEADD(day, 0, ...): This takes the result of the DATEDIFF and adds it back to 0, resulting in the same date but in a datetime2 format.

CAST(... AS DATETIME): This ensures that the result aligns with the datetime2 type.

Lastly, you add the adjusted Time value using a similar method to accurately merge them.

Step 2: Running the Query

To effectively execute the process:

Open your SQL Server Management Studio (SSMS).

Select the database where your Orders table is located.

Paste the UPDATE SQL query into the query window.

Execute the query.

Step 3: Validation

After running the update, verify that the OrderDate column now contains the correctly combined values of Date and Time. You can do this with a simple SELECT query:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Clean Up

With the values successfully combined, you can proceed to remove the old Date and Time columns:

[[See Video to Reveal this Text or Code Snippet]]

Final Thoughts

In summary, combining separate Date and Time columns into a single DateTime column can significantly streamline your database queries and data management. It is essential to ensure that before making such changes, you have backups of your data and have thoroughly tested the queries to avoid data loss.

By following the outlined steps, you can enhance the usability of your database effectively and efficiently. Happy querying!