最近我的用python + flask搞了一个小项目,ORM用到的是SQLAlchemy。python
SQLAlchemy的查询方式很是灵活,你所能想像到的复杂SQL 语句,基本上均可以实现。这里简单的总结一下经常使用的查询技巧。sql
db.session.query(User).filter( and_( or_(User.name==name1,User.name==name2), or_(User.status==1,User.status==2) ), User.active==1 ).first()
if filter_type == 1: search = and_(GameRoom.status ==1,or_( and_(GameRoom.white_user_id == user_id, GameRoom.active_player == 1), and_(GameRoom.black_user_id == user_id, GameRoom.active_player == 0))) elif filter_type == 2: search = and_(GameRoom.status ==1,or_( and_(GameRoom.white_user_id == user_id, GameRoom.active_player == 0), and_(GameRoom.black_user_id == user_id, GameRoom.active_player == 1))) elif filter_type == 3: search = GameRoom.create_by == user_id db.session.query(GameRoom).filter(search).all()
session.query(User, Address).filter(User.id == Address.user_id).all() session.query(User).join(User.addresses).all() session.query(User).outerjoin(User.addresses).all()
black_user = orm.aliased(User) white_user = orm.aliased(User) db.session.query( GameRoom, black_user.score.label("black_score"), white_user.score.label("white_score") ).outerjoin(black_user,GameRoom.black_user_id==black_user.user_id).outerjoin( white_user,GameRoom.white_user_id==white_user.user_id).filter( GameRoom.id==room_id ).all()
session.query(User.name, func.count('*').label("user_count")).group_by(User.name).all() session.query(User.name, func.sum(User.id).label("user_id_sum")).filter(func.to_days(User.create_date)==func.to_days(func.now())).group_by(User.name).all()
子查询。 数据库
stmt = db.session.query(Address.user_id, func.count('*').label("address_count")).group_by(Address.user_id).subquery() db.session.query(User, stmt.c.address_count).outerjoin((stmt, User.id == stmt.c.user_id)).order_by(User.id).all()
sql ="""select b.user_id,b.user_name,b.icon,b.score,a.add_score from (select user_id, sum(score_new - score_old) as add_score from user_score_log where year(create_date)=year(now()) and month(create_date)=month(now()) group by user_id) a join users b on a.user_id=b.user_id order by a.add_score desc limit 50""" list_top = db.session.execute(sql).fetchall()
pagination = GameMessage.query.filter(GameMessage.game_id==game_id).\ order_by(GameMessage.id.desc()).\ paginate(page, per_page=20, error_out=True) pages = pagination.pages total = pagination.total items = pagination.items
总的来讲,SQLAlchemy是我用过的最好的ORM 框架之一(其实我最熟的是.net,python也只用过这一个ORM工具)。基本上常见的SQL 语句,这里都已经实现。若是你的查询实在太复杂的,可能须要用存储过程来实现,直接运行SQL也不失为一种简便的方法。flask