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.
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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.
How 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.
Understanding 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.
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.
A 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.
A 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.
How ARRAY_FILL() Works in PostgreSQL
In PostgreSQL we can use the array_fill() function to create an array filled multiple instances of a given value.
We pass the value to populate as the first argument, followed by the length of the desired array. The resulting array replicates the first argument as specified by the length in the second argument.
We also have the option of passing a third argument to specify the lower bound values of each dimension of the array.
Using ARRAY_TO_STRING() in PostgreSQL
In PostgreSQL we can use the array_to_string() function to convert an array to a string. It converts each array element to its text representation (if needed), and then concatenates all elements using the given delimiter.
Any null values are omitted from the result, but we do have the option of replacing any null values with a given text value.