The most common approach is to manually create a header string, append it to your data table, and then use GUI_DOWNLOAD .
SAP provides built-in tools to handle the conversion and download process more efficiently: FM SAP_CONVERT_TO_CSV_FORMAT: Get Table Header download csv file with header in sap
Loop through your data table, concatenate each row's fields into a single string separated by commas, and append them to your string table. The most common approach is to manually create
Use cl_gui_frontend_services=>gui_download to save the string table to your local PC. Example Logic: append it to your data table
You need two tables: one for your raw data and a "string" table for the final CSV content.