Capturing Particular Value from a String
In this blog post, we will explore how to capture a particular part of an integer value from a string. We will delve into the world of regular expressions and string manipulation techniques to achieve this goal.
Background
When working with data that contains strings in various formats, it’s common to encounter situations where you need to extract specific information from those strings. In this case, we’re dealing with a column attbr that contains VAT numbers as strings, but they are formatted in such a way that extracting the actual VAT number is not straightforward.
Sample Data
Let’s take a closer look at the sample data provided:
{"SRCTAXAMT":"11300",เอ็ก10110","TAXAMT":"11300","LOGID":"190301863","VAT_NUMBER":"0835546003122"}
{"SRCTAXAMT":"11300", กรุงค10110","TAXAMT":"11300","LOGID":"190301863","VAT_NUMBER":"0835546003122"}
........ ... ...
{"SRCTAXAMT":"11300", กรุงค10110","TAXAMT":"11300","LOGID":"190301863","VAT_NUMBER":" "}
As you can see, the VAT numbers are embedded within a string that also contains other information. To extract just the VAT number from each string, we’ll need to use some clever string manipulation techniques.
Solution
One possible solution involves using regular expressions and string manipulation functions to achieve this goal.
Using regexp_substr and regexp_replace
In the provided SQL query, the following line of code is used:
select id,
2 regexp_substr(regexp_substr(attbr, 'VAT_NUMBER":"(\d+)?'), '\d+$') vat
from test;
Let’s break down what’s happening here.
The first regexp_substr function is used to extract the VAT number from each string. The regular expression 'VAT_NUMBER":"(\d+)?' matches the string “VAT_NUMBER”: followed by an optional group of digits (represented by \d+). This effectively extracts the VAT number from each string, including any leading or trailing whitespace.
The second regexp_substr function is used to extract only the numerical part of the VAT number. The regular expression \d+$ matches one or more digits at the end of a string (\d+ matches one or more digits, and $ anchors the match to the end of the string).
By using these two functions together, we’re able to capture the actual VAT number from each string.
How It Works
Here’s a step-by-step explanation of what happens when you run this SQL query:
- The first
regexp_substrfunction extracts the VAT number from each string, including any leading or trailing whitespace. - The second
regexp_substrfunction extracts only the numerical part of the VAT number (i.e., the digits at the end of the string). - The extracted VAT numbers are then returned as a result set.
Example Use Cases
This technique can be applied to various scenarios where you need to extract specific information from strings, such as:
- Extracting phone numbers from a string
- Parsing dates in a specific format
- Capturing credit card numbers from a string
Conclusion
In this blog post, we explored how to capture a particular part of an integer value from a string using regular expressions and string manipulation techniques. We saw how the regexp_substr function can be used to extract the VAT number from each string, followed by another regexp_substr function to extract only the numerical part of the VAT number.
By mastering these techniques, you’ll become more proficient in working with strings and extracting specific information from them.
Common Regular Expressions
Before we wrap up this blog post, let’s take a look at some common regular expressions that might be useful for string manipulation:
\d+matches one or more digits\w+matches one or more word characters (letters, numbers, and underscores)[a-zA-Z]matches any letter (uppercase or lowercase)[^a-zA-Z0-9]matches any non-letter, non-digit character$anchors the match to the end of a string^anchors the match to the beginning of a string
These regular expressions can be used in various contexts, such as extracting phone numbers from strings or parsing dates in specific formats.
Conclusion
Regular expressions and string manipulation functions are powerful tools for working with strings. By mastering these techniques, you’ll become more proficient in extracting specific information from strings and solving complex data processing problems.
In the next blog post, we’ll explore more advanced regular expression techniques and their applications in string manipulation.
Frequently Asked Questions
- Q: What is a regular expression? A: A regular expression is a pattern used to match characters in a string.
- Q: Why do I need to use regular expressions? A: Regular expressions are useful for tasks such as data validation, extraction, and replacement.
- Q: Are regular expressions case-sensitive? A: No, most programming languages make regular expressions case-insensitive by default.
Additional Resources
For more information on regular expressions, check out the following resources:
Last modified on 2023-07-26