How to Retrieve Yesterday's Records in Google BigQuery Using Timestamp Comparison

Discover how to effectively compare timestamps in Google BigQuery to retrieve records from yesterday's date. This guide provides clear solutions and best practices for accurate querying.
---

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: Google BigQuery timestamp comparison

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Retrieve Yesterday's Records in Google BigQuery Using Timestamp Comparison

When working with databases, particularly in Google BigQuery, it’s common to encounter challenges when trying to filter records based on dates and timestamps. A frequent question that arises is: How can I retrieve records logged yesterday from a table with a timestamp column? Let’s delve into an effective solution to this problem.

Understanding the Problem

Suppose you have a table named tbl1, with columns for name, surname, and log_date, where log_date is a timestamp type. You need to filter the records to get only those entries that were logged yesterday.

Many users struggle with comparing timestamps, especially when attempts to extract dates result in errors.

The Core Issue

The main confusion often stems from attempting to compare a timestamp (log_date) with a date extracted from the current timestamp. It’s crucial to note that a direct comparison between these different data types can lead to unexpected results or errors.

Effective Solution

Correct SQL Query

To fetch records that were logged yesterday, use the following SQL query:

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

Breakdown of the Query

DATE(log_date): This extracts the date part from the log_date timestamp.

EXTRACT(DATE FROM CURRENT_TIMESTAMP()): This retrieves the current date.

DATE_ADD(..., INTERVAL -1 DAY): This adjusts the current date to get yesterday's date.

Comparison: The equality operator (=) is used here instead of the greater-than operator (>). Using = ensures that you only fetch records from yesterday, avoiding records from today.

Additional Tip

Instead of using DATE_ADD with a -1 value, you could employ DATE_SUB. While the latter may enhance readability, sticking with your original code format helps establish a better connection to the problem at hand.

Conclusion

Retrieving yesterday’s records based on timestamps in Google BigQuery can be straightforward if you ensure that you're comparing similar data types. By utilizing the right SQL query and understanding how to manipulate dates and timestamps, you can efficiently gather the data you need.

With this guidance, you should be equipped to implement timestamp comparisons successfully in your own BigQuery projects. Happy querying!