The current completion proposal framework does not seem to support table aliases.
select a.name from employees a where a.last_name = 'Smith'
This patch introduces support for finding the column names for an alias with the following notes:
- if table is not found, then considers it a possible alias and looks for the word previously in the statement.
- if the word is found, uses the previous word unless it is AS in which case the next previous word is used