Group By aggregate string function

PostgreSQL 10.x

Below is my situation.  I need some time of aggregate string function that when it finds multiple string values it will order them based on a preferred preference.  Example:  “admin”, then “manager” then “…”.

Table T
fk_id int – foreign key
user_id  text
role text  - possible values could be “admin” and “manager”

Primary key (fk_id, user_id, role)

Sample data:

  1.  lance  admin
1     lance manager
87   bob   manager
98   tom admin
104 tom manager

SELECT fk_id, user_id, some-aggregate-string-function(role, “admin”, “manager”)  FROM T  WHERE user_id = ‘lance’ GROUP BY fk_id, user_id;

When selecting data if there are multiple rows within the group by then aggregate the result based on a priority for role of “admin” first, “manager” second, etc.

Expected Result:
1 lance admin

Ignores the second record with lance in it because it contains admin.

THANKS!


LANCE CAMPBELL<https://directory.illinois.edu/person/lance>
Software Architect

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