REGEXP_REPLACE : How to use a column value in the regex

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

REGEXP_REPLACE : How to use a column value in the regex

PG Bug reporting form
The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/functions-matching.html
Description:

The documentation doesn't talk about any regex syntax for using a column
from the db in the pattern. There is no mention if this is NOT supported.
All the examples are using static string and none using a DB column
values.
e.g. I have a field *portfolio* which had data like CloudPlatform (Public),
CloudPlatform (Private), MobilePlatfom (Public),.. etc
These values are coming from another table *platformtypes" which has these
values Public, Private, Hybrid...etc.
I want to replace these types from the portfolio names, i was able to do it
using string
*SELECT
Portfolios.PortfolioName,REGEXP_REPLACE(Portfolios.PortfolioName,'(\(Public\))',''),
but I would like to use something  like
*REGEXP_REPLACE(Portfolios.PortfolioName,'(\(platformtypes.Name\)),'')*
Reply | Threaded
Open this post in threaded view
|

Re: REGEXP_REPLACE : How to use a column value in the regex

Bruce Momjian
On Mon, Feb 17, 2020 at 06:37:11AM +0000, PG Doc comments form wrote:

> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/12/functions-matching.html
> Description:
>
> The documentation doesn't talk about any regex syntax for using a column
> from the db in the pattern. There is no mention if this is NOT supported.
> All the examples are using static string and none using a DB column
> values.
> e.g. I have a field *portfolio* which had data like CloudPlatform (Public),
> CloudPlatform (Private), MobilePlatfom (Public),.. etc
> These values are coming from another table *platformtypes" which has these
> values Public, Private, Hybrid...etc.
> I want to replace these types from the portfolio names, i was able to do it
> using string
> *SELECT
> Portfolios.PortfolioName,REGEXP_REPLACE(Portfolios.PortfolioName,'(\(Public\))',''),
> but I would like to use something  like
> *REGEXP_REPLACE(Portfolios.PortfolioName,'(\(platformtypes.Name\)),'')*

Sure, you can do it ('a' -> 'X'):

        CREATE TABLE TEST (x text);
        INSERT INTO test VALUES ('a');
        SELECT REGEXP_REPLACE(relname, x, 'X') FROM pg_class, test;
                        regexp_replace
        -----------------------------------------------
         pg_toXst_36526
         pg_toXst_36526_index
         test
         pg_stXtistic
         pg_type
         pg_toXst_2600

You can also combine column names with literal text ('ta' -> 'YY'):

        SELECT REGEXP_REPLACE(relname, 't' || x, 'YY') FROM pg_class, test;
                        regexp_replace
        -----------------------------------------------
         pg_toast_36526
         pg_toast_36526_index
         test
         pg_sYYtistic

I didn't think it was worth documenting this.

--
  Bruce Momjian  <[hidden email]>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +