user: ### NOW ANSWER:
Question: What was the 2006 population for the local government area of alexandrina council whose rank was smaller than 19?
Columns: ['Rank', 'Local government area', 'Population 2006 census', 'Population 2007 estimate', 'Growth rate', 'Stat. division/district']
Types: ['real', 'text', 'real', 'real', 'text', 'text']
Sample row: [1.0, 'City of Onkaparinga', 154417.0, 155919.0, '1.0%', 'Adelaide']
SQL:

assistant: SELECT AVG("Population 2006 census") FROM "Table" WHERE "Local government area" = 'alexandrina council' AND "Rank" < 19.0;