Return part of a string with variable length

All we need is an easy explanation of the problem, so here it is.

I have data in a table column like below:

host= port=5432 dbname=database_name user=pglogicaluser
host= port=5432 dbname=database_name2 user=pglogicaluser

I want to write a query to get the database names only like below:


I could come up with something like:

select substring(column_name, '.+dbname=(.*)$') from table_name;

However, I couldn’t figure how to stop the extraction before the user keyword starts.

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

you need to include a space after the regex group that acts as a delimiter to separate the user keyword from the text you want to match. To make the regex match in that case, an additional "any other character" is needed.

substring(column_name, '.+dbname=(.*) .*$') 

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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