How to use the auto complete on an issue (simple query)
Create/Update an issue
Before using the database custom field of type Autocomplete, please make sure the type of the custom field is Autocomplete in the Kepler Administration Page.
Go to an issue in jira and try to edit it first. The database custom fields will appear like any other custom field. When trying to edit an issue, the sql is executed and the results will be filled in the fields.
Try to type the first letter of a possible value and a list of options will appear. From these option one can be selected for the current field. On selection of a main database custom field, the value of the child database custom field is filled in like in the picture below: 
Now that the fields are filled in, the issue can be updated with the provided values.
After updating the issue, the values are displayed as a detail of an issue.
The creation of an issue can be done in a similar way.
Use auto complete for a transition
The provided example involves updating the issue fields when Start Progress is pressed.
This is similar to the update of an issue, still here are some screenshots to explain how to use the database custom fields on transitions.
The value of the field Product Name can be changed to another value like in the screenshot below:
The database child custom field is filled in on selection of the value for the main database custom field. If the button Start Progress is pressed, the values are updated for the database custom fields and the issue goes in the final state of the transition.
For this example it looks like this:
How to use the auto complete on an issue (dynamic query)
Check in the administration page that you have a dynamic sql.
Go to the issue and try to edit it. For this example, it is used the same issue. So it looks like in the following picture on edit.
Let's change the values now, so go directly to the fields Published and Not published, special created for this example. These fields have the id: customfield_11901(Not publiched) and customfield_11900(Published). These are simple jira custom fields, of type "Text Field (< 255 characters)".
Let's type in first jjupin for Published and try to fill in the second value for Not published. At this time, the values for Product Name and Product Id are dynamically changed depending on the value of the field Published as long as Not published. 
In the mean time we can type in a value for Not published as well.
Let's now use the auto completion to see from what values we can choose to change the main database custom field Product Name:
The only option left is the one displayed. This is equals with the value of Published.
In a similar way the auto complete is used for other operation on issues.