我的transactions集合中有以下文档。{txnId:1,amount:200,tags:["monthly","recharge"]},{txnId:2,amount:4000,tags:["monthly","salary"]},{txnId:3,amount:1000,tags:["monthly","waterbill"]},{txnId:4,amount:400,tags:["monthly","electricity"]},{txnId:5,amount:300,tags:["dinner","daily"]}我想获取所有有monthly但没有salary的文档我尝试