## What changes were proposed in this pull request?

This PR makes various minor updates to examples of all language bindings to make sure they are consistent with each other. Some typos and missing parts (JDBC example in Scala/Java/Python) are also fixed.

## How was this patch tested?

Manually tested.

Author: Cheng Lian <lian@databricks.com>

Closes #14368 from liancheng/revise-examples.