Is there a way to systematic way to find out what is using a column in a CDT? We

I would go check the XSD of that CDT and see which database columns are mapped with CDT fields. I think it is also possible that none of the CDT fields are mapped with a DB column, so you wouldn't get that column values in to Appian when you query on that CDT entity.

Thanks for the response. What I meant was I want to know if interface/expression/query rules are using a column.

@alexanderc I don't think that there is an OOTB utility to do so.

I would like to suggest one manual approach as follows which could be elegant when compared to manual process.

1. Obtain the DDL from the datastore in Appian. I guess this could be obtained when you try to publish the data store to a new datasource.
2. Extract the DDL script from the database schema.
3. Compare the sql scripts from both sources, that is, data store and database manually by making use of a text comparison utilities.

Let's see if any other user could suggest much efficient approach when compared to making manual comparisons in each CDT against its associated table.

@alexanderc The only way I have accomplished this in the past is pattern matching the xml of downloaded applications. Ex. look for ri!cdt.columnName or index(ri!cdt, "columnName", null) etc. Its a pretty brute force method and can return a ton of false positives but it gets the job done.