I migrate from Oracle DB to Postgres/MS-SQL and I want to use REGEXP_SUBSTR equivalent with these databases. I need to rewrite this statement to these databases:
SELECT b.id, b.name, b.description, REGEXP_SUBSTR(b.description, '(st|ek)', 1, 1, NULL, 1) substring FROM books b;
I was able to write this statement for PostgreSQL as:
SELECT b.id, b.name, b.description, (SELECT array_to_string(a, '') FROM REGEXP_MATCHES(b.description, '(st|ek) ', 'g') AS f(a) LIMIT 1) substring FROM books b;
However I have no idea how to rewrite to MS-SQL db. I tried to used statement below however bad result is returned for substring column. Is any solution for this issue please?
SELECT b.id, b.name, b.description, (SELECT SUBSTRING(b.description, PATINDEX('(st|ek)', CAST(b.description AS varchar)), LEN(b.description))) substring FROM books b;
Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.
The solution for Postgres is to use
substring('one two three four five' from '(S+)')
one. The biggest difference to Oracle’s
regexp_substring() is that you can’t locate the “nth” occurance directly. To get the second word, you could use:
substring('one two three four five' from 'S+s*(S+)')
If you are trying to access words (separated by whitespace), then splitting the string into an array is another alternative:
(regexp_split_to_array('one two three four five', 's+'))
The above returns the first word,
 would return the second. The regex defines the separator (delimiter) between each element.
Note that Postgres 15 will have a
regexp_substr() that is pretty much identical to Oracle’s implementation.
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0