Hi,
Thats fundamentally against the purpose of a CSV file. A CSV file is defined as a text file, with one row or fewer of column headers, with subsequent records detailing the data of those columns, delimited by a comma. To that effeect if I was to recieve your described file I would reject it, and I would be surprised if anyone willingly accepts it as such. Export each data strcuture to its own file - you would need to document this in any data transfer agreement document anyways.
There are other options out there if you need to ship data as flat file but with structure, JSON and XML can both be used to contain multiple different structures within one file. The question you have to ask is wether its worth the effort, most of the time just create one CSV file per dataset is simplest.
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