get_sql_upsert: compares two data.frames and transforms the delta into SQL...
In awerni/df2sql: transforms data frames to SQL commands

compares two data.frames and transforms the delta into SQL commands

1 2	get_sql_upsert(new_df, old_df, key_col, tablename, add_method = "copy", del_old = FALSE)

`new_df`	A `data.frame` or `tibble` specifiying the database table after the changes
`old_df`	A `data.frame` or `tibble` with the current database table content
`tablename`	The name of the database table to delete from
`add_method`	Specifies the import method (copy (default) or insert)
`del_old`	Boolean flag to specify if missing data in new_df should be deleted