First shot relational algebra -> sql; untested
Add FIXME about Combine ops
Put relational schema into sql.Query.Table
Fix micro-optimization "alias supression"
sql.Query.Table -> sql.Query.Base
sql.Query -> sql.Table
DbConnection.query -> DbConnection.read
Return base table for base queries
Add trivial relational-algebra -> sql tests
Add 'case' test case
Add 'aggregation' test
Add 'order', 'subquery' tests
Add 'quotient' test