Firstly it’s always useful to let the community know what version of OpenIAM you are using and how you are deploying it. Please make sure you let us know these as it might impact the answer you are given.
There are a couple of ways to pull in users from a database. I’m guessing you are using this DB as an authoritative source such as a HR system?
The first way would be to setup a new Synchronization and use “RDBMS” as the sync source and point the managed system at OpenIAM. You can then configure the db so set the connection url and jdbc driver as appropriate. You can find examples and information on how to configure these in some of the older docs at https://docs.openiam.com/docs-4.1.14/html/administration/webconsole/synchronization.htm. Once configured you’ll need to write and put your SQL query e.g. select * from users etc into the SQL Query/Directory Filter box. Because you will be using RDBMS, you will need to supply transformation rules to map the columns from your SQL query to OpenIAM attributes. There is an example transformation groovy script found within /sync/user/db/DBSampleTransformationScript.groovy.
Alternatively you can setup synchronization from a managed system using a connector. There is an jdbc connector which will work in a similar way but you should be able to use a policy map instead. Out of the box there are example configurations for this. Look in the managed system for “JDBC Managed System” and under Synchronization you’ll find an entry “JDBC User Example”.
Hopefully that’s enough info to get you going.