SQLAlchemy中filter()和filter

from:https://segmentfault.com/q/1010000000140472

filter:

apply the given filtering criterion to a copy of this Query, using SQL expressions.e.g.:session.query(MyClass).filter(MyClass.name == 'some name')

filter_by:

apply the given filtering criterion to a copy of this Query, using keyword expressions.e.g.:session.query(MyClass).filter_by(name = 'some name')

确实，filter用类名.属性名，比较用==，filter_by直接用属性名，比较用=不过这个是语法小细节。

个人觉得最重要的区别是filter不支持组合查询，只能连续调用filter来变相实现。而filter_by的参数是**kwargs，直接支持组合查询。比如：

q = sess.query(IS).filter(IS.node == node and IS.password == password).all()对应的sql是

SELECT tb_is.id AS tb_is_id, tb_is.node AS tb_is_node, tb_is.password AS tb_is_password, tb_is.email AS tb_is_email, tb_is.`admin` AS tb_is_admin, tb_is.contact AS tb_is_contact, tb_is.is_available AS tb_is_is_available, tb_is.is_url AS tb_is_is_url, tb_is.note AS tb_is_note FROM tb_is WHERE tb_is.node = %(node_1)s

and后面的条件既不报错，又不生效，很坑。

要实现组合查询，要么连续调用filter：q = sess.query(IS).filter(IS.node == node).filter(IS.password == password).all()

或者直接用filter_by：q = sess.query(IS).filter_by(node=node, password=password).all()

两者都对应sql：

  SELECT tb_is.id AS tb_is_id, tb_is.node AS tb_is_node, tb_is.password AS tb_is_password, tb_is.email AS tb_is_email, tb_is.`admin` AS tb_is_admin, tb_is.contact AS tb_is_contact, tb_is.is_available AS tb_is_is_available, tb_is.is_url AS tb_is_is_url, tb_is.note AS tb_is_note FROM tb_is WHERE tb_is.password = %(password_1)s AND tb_is.node = %(node_1)s

转载于:https://www.cnblogs.com/c-x-a/p/8521328.html