mongodb pymongo：
有两条记录是这样

{"a":"AAA" , "b":[ {"b11": "b11value" ,"b12":"b12value"} , { "b21":"b21value" , "b22":"b22value" } ]}

{"a":"BBB" , "b":[ {"b11": "b11value" ,"b12":"b12value"} , { "b21":"b21value" , "b22":"b22value" } ]}

我想更新a为AAA且b中b11的值为b11value的值为b11111111value:
结果应该是这样：

{"a":"AAA" , "b":[ {"b11": "b11111111value" ,"b12":"b12value"} , { "b21":"b21value" , "b22":"b22value" } ]}

{"a":"BBB" , "b":[ {"b11": "b11value" ,"b12":"b12value"} , { "b21":"b21value" , "b22":"b22value" } ]}

以及把a为AAA且b中b11的值为b11value的（b11删除）
结果应该是这样：

{"a":"AAA" , "b":[ { "b21":"b21value" , "b22":"b22value" } ]}

{"a":"BBB" , "b":[ {"b11": "b11value" ,"b12":"b12value"} , { "b21":"b21value" , "b22":"b22value" } ]}

一个更新，一个是删除
这两个怎么写？
sql语句应该怎么写？谢谢