Update:另请参见SQLAlchemy用法配方here
据我所知,创建(只读非materialized )视图是不支持开箱即用的.但是在SQLAlchemy 0.7中添加这个功能很简单(类似于我给出的here个示例).你只需要写一个compiler extension CreateView
.有了这个扩展,您就可以写了(假设t
是一个包含id
列的表对象)
createview = CreateView('viewname', t.select().where(t.c.id>5))
engine.execute(createview)
v = Table('viewname', metadata, autoload=True)
for r in engine.execute(v.select()):
print r
以下是一个有效的例子:
from sqlalchemy import Table
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.sql.expression import Executable, ClauseElement
class CreateView(Executable, ClauseElement):
def __init__(self, name, select):
self.name = name
self.select = select
@compiles(CreateView)
def visit_create_view(element, compiler, **kw):
return "CREATE VIEW %s AS %s" % (
element.name,
compiler.process(element.select, literal_binds=True)
)
# test data
from sqlalchemy import MetaData, Column, Integer
from sqlalchemy.engine import create_engine
engine = create_engine('sqlite://')
metadata = MetaData(engine)
t = Table('t',
metadata,
Column('id', Integer, primary_key=True),
Column('number', Integer))
t.create()
engine.execute(t.insert().values(id=1, number=3))
engine.execute(t.insert().values(id=9, number=-3))
# create view
createview = CreateView('viewname', t.select().where(t.c.id>5))
engine.execute(createview)
# reflect view and print result
v = Table('viewname', metadata, autoload=True)
for r in engine.execute(v.select()):
print r
如果你愿意,你也可以专门学习一种方言,例如.
@compiles(CreateView, 'sqlite')
def visit_create_view(element, compiler, **kw):
return "CREATE VIEW IF NOT EXISTS %s AS %s" % (
element.name,
compiler.process(element.select, literal_binds=True)
)