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Learn how to efficiently convert string fields to date types in BigQuery and troubleshoot common errors in the process.
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How to Fix String to Date Conversion Errors in Big Query

When working with data in BigQuery, one common challenge many users face is converting string representations of dates into actual date types. In this guide, we will address a specific issue related to this task, particularly when dealing with dates formatted as "July 19, 2020" or "August 8, 2020". If you've encountered errors like "Failed to parse input string" or "Invalid Date" while trying to execute your queries, you are not alone! Let’s explore how to tackle this problem effectively.

The Problem

You may find yourself in a situation where you have a string field from a table that contains date information but encounters errors when you try to cast it into a date type in your view. The common error messages you might see include:

"Failed to parse input string 'July 19, 2020'"

"Invalid Date: August 8, 2020"

These issues often arise due to the format of the date string. BigQuery requires dates to be in a specific format to interpret them correctly, and casting alone may not suffice.

Solution: Use PARSE_DATE Function

Instead of using the CAST function, you should opt for the PARSE_DATE function, which is designed for converting formatted date strings into date formats efficiently. This method allows you to specify the exact format of your date string, improving accuracy and reducing errors.

Here's the correct approach:

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

Breaking It Down:

%B: Matches the full month name (e.g., "July")

%d: Matches the day of the month as a zero-padded decimal (e.g., "19")

%Y: Matches the year in four digits (e.g., "2020")

Example Query

Let's look at a full example where we parse a string date using a simplified dataset:

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

Expected Output:

After running the query, you should see something like this:

Rowdate_as_date12020-07-1922020-08-08This output confirms that the strings have been successfully converted into date formats, enabling you to perform further analysis or queries without errors.

Conclusion

Converting strings to dates in Big Query doesn't have to be a daunting task. By using the PARSE_DATE function along with the appropriate format specifiers, you can effectively eliminate errors and work with your date data seamlessly.

If you continue to encounter issues, double-check the format of your date strings and ensure they align with the format you are specifying in the PARSE_DATE function. Happy querying!