What is the total number of bikes that can be hold in Redwood City before 2014.
total number of bikes that can be hold = MAX(dock_count); before 2014 refers to year(installation_date)<2014;
SELECT SUM(CASE WHEN city = 'Redwood City' AND SUBSTR(installation_date, -4) < '2014' THEN dock_count ELSE 0 END) NUM FROM station