Скачать или смотреть Resolving the ANY Function Issue with varchar[] in PostgreSQL

Encountering issues with the `ANY` function on `varchar[]` in PostgreSQL? Learn how to resolve the problem and properly structure your queries!
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This video is based on the question https://stackoverflow.com/q/72827922/ asked by the user 'Ali Abdi' ( https://stackoverflow.com/u/3677021/ ) and on the answer https://stackoverflow.com/a/72827991/ provided by the user 'Laurenz Albe' ( https://stackoverflow.com/u/6464308/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the ANY Function in PostgreSQL for varchar[] Arrays

If you’ve been working with PostgreSQL arrays, you may have encountered a frustrating issue when trying to use the ANY function with a varchar[] column. This post aims to clarify the problem you might face and provide a clear solution to ensure your queries work as intended.

The Problem

Imagine you have a product table that includes a column named excluded_company_codes, which stores company codes in the form of an array of type varchar[]. For instance, if you run the following SQL command:

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You might receive output like this:

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Now, if you’re trying to check whether the company code '10' exists within that array using the ANY function, you might run into some unexpected behavior:

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Instead of getting a true result, you’ll notice that it returns false, which can be quite puzzling.

The Solution

Understanding the Issue

What’s happening here is that the string comparison is failing due to the way PostgreSQL handles string literals in arrays, particularly those with single quotes. The company code '10' in the array is being treated differently than how you're referencing it in your query.

Correctly Referencing Strings with Quotes

To properly check for the existence of '10' in the array, you need to account for the additional single quotes that PostgreSQL inserts around string values. You have two options to rectify this issue:

Double the Quotes: You can write your query with double quotes around the string you are checking against:

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Here, you'll notice that the company code is surrounded by three single quotes on each side. This syntax allows PostgreSQL to correctly interpret your intention to search for the string '10'.

Use Dollar Quoting: If you want to simplify the usage of quotes and avoid the doubling, you can employ PostgreSQL’s dollar quoting approach. Here’s how you would do it:

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This results in a cleaner and more readable query while achieving the same effect.

Conclusion

In summary, when working with the ANY function on varchar[] arrays in PostgreSQL, it's crucial to pay close attention to how strings are formatted. The two solutions provided above—using doubled quotes or dollar quoting—will enable you to perform your array searches correctly and avoid frustrating comparisons that lead to false outcomes.

Exploring and understanding how PostgreSQL handles strings in different contexts gives you the power to write effective and efficient queries. Happy querying!