Lets the user choose a value from a dropdown filled with predefined values.
The values can be combined with friendly labels, and in that case
the labels will be displayed to the user instead of the value.
For stable and predictable behaviour, always use an explicit ORDER BY clause.
The name depends on the usage. If the control is used to retrieve values from a lookup table then the procedure should be named "<Schema>.<LookupTable>Dropdown". If it is not and the values are not directly linked to rows in a table or the functionality is specific for the current field (say for instance a choice between each of the last six years) then the procedure should be named "<Schema>.<Table><Field>_Dropdown".