Скачать или смотреть Convert Day of Week Name to Day of Week Number in Vertica

Learn how to efficiently convert a `day of week name` (like MONDAY) into its corresponding `number` (like 1) using SQL in Vertica.
---
This video is based on the question https://stackoverflow.com/q/64606631/ asked by the user 'java-dev-ua' ( https://stackoverflow.com/u/8483171/ ) and on the answer https://stackoverflow.com/a/64606783/ provided by the user 'Gordon Linoff' ( https://stackoverflow.com/u/1144035/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Convert day of week name to day of week number Vertica

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Converting Day of Week Names to Numbers in Vertica

When working with databases, especially in SQL environments like Vertica, you often encounter various types of data formats. One such scenario is when you need to convert a day of week name, such as 'MONDAY', into its corresponding number representation (Monday being 1, Tuesday being 2, and so forth). This conversion can be crucial when performing time-related calculations or organizing data by weekdays. In this post, we’ll explore a few methods to achieve this in Vertica.

The Challenge

You may already know that with the following SQL commands, you can achieve certain functionalities:

To get the day of the week name, you can use:

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

To retrieve the day of the week as a number, you can use:

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

The actual challenge, though, is converting the day name directly into a day number. For example, transforming 'MONDAY' into 1 directly in SQL.

Solutions to Convert Day Names to Numbers

Here are two effective methods you can utilize in Vertica to perform this conversion.

Method 1: Using a CASE Expression

One straightforward approach is to utilize a CASE statement. This is an explicit way of defining what number corresponds to each day of the week. Here’s how you can do it:

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

In the above SQL snippet, you replace 'MONDAY' with your desired day name, and it will return the corresponding number.

Method 2: Using Arrays

Another, more concise method is leveraging arrays. This option is elegant and can simplify your queries, especially if you plan to perform the conversion dynamically. Use the array_find function along with an array of days to get your result:

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

Here, array_find searches for the specific day in the provided array and returns its index, which starts at 0. Therefore, we add 1 to get the expected day number.

Conclusion

Converting day names into their corresponding numbers in Vertica can be done using either a CASE expression for straightforward use or an array function for a more dynamic approach. Choose the method that best fits your needs based on how you plan to use the data. By utilizing these methods, you can effectively and efficiently manage your time-related data in Vertica.

Feel free to reach out with your experiences or to ask any questions regarding SQL in Vertica!