You can Alter the definition of a table by (in the Database Explorer window) clicking on a table then the Alter button in the Admin Toolbar.
You will be shown a window such as the following:
You will not be able to amend every part of a table's definition. Different databases have different rules about which parts of the table definition can be altered.
attributes that you are able to change will be in white. Non-changeable values are in grey.
once you have amended a value, it will be shown in yellow. This indicates a pending change.
if your database allows you to delete columns, you will have a button Delete Column - click on this to mark the column for deletion. A pending deletion is shown in yellow with strike-through font. If you subsequently click the column, the Undelete Column button will be displayed. Clicking on this will take the column out of delete-pending status.
clicking on Preview shows you the SQL that AQT will run for applying the changes that you have made.
Applying the Changes
Click on Run to run the changes.
AQT will apply the changes to the database by running a series of SQL statements.
AQT keeps track of whether each change is successful. If so, the value you have changed is taken out of change-pending status (and returns to being white). Any columns or objects you have deleted are removed from the grids.
If the change is not successful, the change remains in change-pending or delete-pending status; you can then correct your changes and click on Run again.
Can click on Refresh to re-load the table definition. This can be useful after you have made as series of changes.