Document DML statements #7319
Description
Is your feature request related to a problem or challenge?
DataFusion now supports basic INSERT and COPY statements.
Describe the solution you'd like
We should update https://arrow.apache.org/datafusion/user-guide/sql/index.html to reflect this
Examples are in https://github.com/apache/arrow-datafusion/blob/main/datafusion/sqllogictest/test_files/copy.slt and https://github.com/apache/arrow-datafusion/blob/main/datafusion/sqllogictest/test_files/insert_to_external.slt
Describe alternatives you've considered
No response
Additional context
No response