Scott, I'm assuming you're trying to create a single (possibly sparse) table for all the incoming JSON records, and that you do not know the total set of fields ahead of time. If you do know the fields ahead of time, you can create the table ahead of time and use the JoltTransformJSON processor to add default values for any missing fields in any records. You may also be able to do this with ConvertRecord.
If you do not know the total set of fields ahead of time, how will you know you have "enough" records in the flow whose fields fully define the table? If you won't ever know for sure that your flow contains records whose values fully define the table, you'd have to try to add missing columns as they are encountered (see  for SQL Server commands to do this). That can get messy, you'd have to pull the field names out into attributes and use PutSQL's SQL Statement property (added in NiFi 1.5.0) with NiFi Expression Language to execute the SQL command for adding a column if it doesn't exist. Otherwise you'd have to use Wait/Notify or some other barrier stuff to ensure the column was added before a record with that field is pushed to the database. Basically it's very difficult to do if you don't know all the possible table columns up front. If you are consuming from a Web service, I would hope their API at least documents all possible fields, and you could create a table from that. Regards, Matt  https://stackoverflow.com/questions/8870802/add-a-column-to-a-table-if-it-does-not-already-exist On Sat, Mar 10, 2018 at 7:18 PM, scott <tcots8...@gmail.com> wrote: > Hello NiFi community, > > I have a problem I've been working on that I was hoping to get some > suggestions for a solution. I'm ingesting a dump of json records from a web > service periodically. The json sometimes comes with some fields missing. My > goal is to insert the data into a SQLServer DB after dynamically creating > the table based on the fields in the json records. The problem is that when > I use the list of fields from a record that is missing some fields, I get > errors when I try to insert. How do I take all the fields from all records > in my dump and then create a unique list of all fields for me to create the > table with? > > > Thanks, > > Scott >