java.lang.RuntimeException: For update, Schema must have a key

This is a famous Talend runtime Exception that a novice could run into several times especially when using an DBoutput component and updating the rows. Talend Forums are not quite helpful in resolving this issue. The fix is very straightforward but very unintuitive to know about it in the first attempt.

The fix involves checking the "Update-Key" found in the Advanced Settings of the Component view.

Above is the screenshot of how to fix the Exception. Go to the "Component" tab --> "Advanced Settings" --> Update Key

Check the appropriate column in the check boxes under the update key heading. You might have to scroll down the page to find this setting.