Sorry, we don't have an e-r diagram, but the database columns are all logically-named (i.e.article_id in one table will always map to an article_id in the articles table). The only tricky parts are:[list][*]Depending on your DBMS, you may need to set auto-increment sequences so that they don't carry on incrementing, potentially overwriting your merged-in IDs.[*]There are a few columns named assoc_id in the database; these will map to IDs in different tables depending on the associated type / assoc_type columns.
Have you had a look at the technical reference? It's available from the "Documentation" section of the OJS website.
If you only need to keep your published content (i.e. workflow and other data isn't important), you could consider exporting and importing via the Import/Export interface.
Open Journal Systems Team
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