PostgreSQL has an extensive collection of built-in string functions that allow us to manipulate text values. One task we might want to perform is to extract a substring from a larger string. Fortunately, PostgreSQL caters for our needs with at least two functions that make this a breeze.
Continue readingA Quick Look at PostgreSQL’s REVERSE() Function
In PostgreSQL, we can use the reverse() function to return a specified string with its characters reversed. In other words, the string is returned with its characters in the reverse order to how we provided them.
Understanding PostgreSQL’s REGEXP_MATCHES() Function
In PostgreSQL, the regexp_matches() function returns substrings that match a given POSIX regular expression in a given string. We can specify that all matches are returned or just the first match. If all matches are returned, each is returned in a separate row.
We pass the string as the first argument and the pattern as the second argument. We can also provide a flag as an optional third argument, which determines how the function behaves.
Each returned row is a text array containing the whole matched substring or the substrings matching parenthesised subexpressions of the pattern.
Continue readingHow REGEXP_MATCH() Works in PostgreSQL
In PostgreSQL, the regexp_match() function returns a text array containing substrings that match a given POSIX regular expression in a given string. Only the first match is returned (to return all matches, use regexp_matches() instead).
We pass the string as the first argument and the pattern as the second argument. We can also provide a flag as an optional third argument, which determines how the function behaves.
Continue readingUnderstanding PostgreSQL’s pg_input_error_info() Function
PostgreSQL has a pg_input_error_info() function that allows us to see the error details that would be returned if we were to pass an invalid value for the specified data type.
Basically it tests whether the given string is valid input for the specified data type. If invalid, it returns the details of the error that would have been thrown. If valid, the result is null.
An Introduction to pg_input_is_valid() in PostgreSQL
In PostgreSQL, the pg_input_is_valid() function tests whether the given string is valid input for the specified data type.
It returns a boolean value of either true or false.
This function only works if the data type’s input function has been updated to report invalid input as a “soft” error.
Continue readingFix “function array_shuffle(numeric) does not exist” in PostgreSQL
If you’re getting an error that reads “function array_shuffle(numeric) does not exist” when using the array_shuffle() function in PostgreSQL, it’s probably because the argument you’re passing to the function is not an array.
More specifically, this error message implies that you’re passing a numeric type. The same error can occur when passing other non-array types (such as integer), but the solution is the same.
The argument for this function must be an array.
To fix this error, replace the numeric value with an array value when calling the array_shuffle() function.
Using ARRAY_REPLACE() in PostgreSQL
In PostgreSQL we can use the array_replace() function to replace a specified element (or elements) in an array with another element.
The first argument is the array, the second is the element to replace, and the third is the element to replace it with.
Continue readingA Quick Overview of PostgreSQL’s REGEXP_SUBSTR() Function
In PostgreSQL, we can use the regexp_substr() function to return a substring from a string based on a POSIX regular expression.
We can get the first occurrence or any other subsequent occurrence that matches the expression.
Continue readingA Quick Look at TRIM_ARRAY() in PostgreSQL
In PostgreSQL, we can use the trim_array() function to trim a given number of elements from the end of an array.
The first argument is the array, and the second is the number of elements to trim.
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