Скачать или смотреть Handling NULL Values in DATE Type Columns in Google BigQuery SQL Queries

Learn how to effectively manage `NULL` values in `DATE` type columns within Google BigQuery queries to avoid errors and enhance your data checks.
---
This video is based on the question https://stackoverflow.com/q/63721094/ asked by the user 'amaturePy' ( https://stackoverflow.com/u/11393305/ ) and on the answer https://stackoverflow.com/a/63722378/ provided by the user 'aemon4' ( https://stackoverflow.com/u/12852090/ ) 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: how to handle NULL values in DATE type column on where statement

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.
---
Handling NULL Values in DATE Type Columns in Google BigQuery SQL Queries

Working with databases often brings us face-to-face with the challenge of handling NULL values. If you have a DATE type column in Google BigQuery, querying that column can lead to errors and confusion if not handled correctly. In this guide, we will explore a common problem regarding NULL values in DATE columns and how to build a query that effectively checks for non-null entries.

The Problem

You have a Google BigQuery table containing a cv_date column of type DATE, and you want to determine if there are any non-null dates for a specific luid. However, an attempt to check for non-null dates might generate an error, such as:

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

This occurs when the SQL query does not correctly filter NULL values. This common scenario leads many developers to seek clarity on how to handle NULL in DATE fields in SQL queries effectively.

The Solution

To resolve this issue, you must modify your SQL query to properly handle the NULL values and ensure that your check for the existence of a non-null cv_date is correctly formulated. Below, we will break down the necessary changes step-by-step.

Formulating the Query

Instead of checking if cv_date is not equal to an empty string, you want to verify that it is not NULL. In SQL, you can use the IS NOT NULL condition to achieve this. The corrected SQL query should resemble the following:

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

In this query:

luid is the identifier you're checking against.

cv_date IS NOT NULL as date will return TRUE if there exists a non-null date for the specific luid, and FALSE otherwise.

Integrating the Query in Python

When implementing this in your Python application using Flask, you can follow this adjusted code snippet:

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

Key Points to Remember

IS NOT NULL condition should be used to check for non-null values in DATE columns.

Avoid comparing DATE fields to empty strings—this will lead to errors.

Properly format your SQL string to ensure that it executes correctly within your application logic.

Conclusion

Handling NULL values in DATE type columns can be tricky, but understanding how to write appropriate SQL queries can simplify this process. By using the IS NOT NULL check, you can determine whether a valid date entry exists for your specified identifier without encountering type errors. Implement these practices in your Google BigQuery SQL queries for smoother data management and exploration.

If you have any additional questions about handling NULL values or SQL queries in general, feel free to reach out in the comments below!