sql: join on SQL objects
WIP - clean join
wip: clean sql join
complex joins significantly cleaner
projection of join test
sql: lower_column test
sql: remove redundant projection code
sql: selections when predicate is a select
Merge branch 'master' into sql-join-clean
py26 fix with dict comprehension
Merge pull request #662 from mrocklin/sql-join-clean

Cleaner SQL joins