左边是mongodb查询语句,右边是sql语句。对照着用,挺方便。
db.users.find() select*fromusers
db.users.find({"age":27}) select*fromuserswhereage=27
db.users.find({"username":"joe","age":27}) select*fromuserswhere"username"="joe"andage=27
db.users.find({},{"username":1,"email":1}) selectusername,emailfromusers
db.users.find({},"_id":0}) //nocase//即时加上了列筛选,_id也会返回;必须显式的阻止_id返回
db.users.find({"age":{"$gte":18,"$lte":30}}) select*fromuserswhereage>=18andage<=30 //$lt(<)$lte(<=)$gt(>)$gte(>=)
db.users.find({"username":{"$ne":"joe"}}) select*fromuserswhereusername<>"joe"
db.users.find({"ticket_no":{"$in":[725,542,390]}}) select*fromuserswhereticket_noin(725,390)
db.users.find({"ticket_no":{"$nin":[725,390]}}) select*fromuserswhereticket_nonotin(725,390)
db.users.find({"$or":[{"ticket_no":725},{"winner":true}]}) select*formuserswhereticket_no=725orwinner=true
db.users.find({"id_num":{"$mod":[5,1]}}) select*fromuserswhere(id_nummod5)=1
db.users.find({"$not":{"age":27}}) select*fromuserswherenot(age=27)
db.users.find({"username":{"$in":[null],"$exists":true}}) select*fromuserswhereusernameisnull //如果直接通过find({"username":null})进行查询,那么连带"没有username"的纪录一并筛选出来
db.users.find({"name":/joey?/i}) //正则查询,value是符合PCRE的表达式
db.food.find({fruit:{$all:["apple","banana"]}}) //对数组的查询,字段fruit中,既包含"apple",又包含"banana"的纪录
db.food.find({"fruit.2":"peach"}) //对数组的查询,字段fruit中,第3个(从0开始)元素是peach的纪录
db.food.find({"fruit":{"$size":3}}) //对数组的查询,查询数组元素个数是3的记录,$size前面无法和其他的操作符复合使用
db.users.findOne(criteria,{"comments":{"$slice":10}}) //对数组的查询,只返回数组comments中的前十条,还可以{"$slice":-10},{"$slice":[23,10]};分别返回最后10条,和中间10条
db.people.find({"name.first":"Joe","name.last":"Schmoe"})//嵌套查询
db.blog.find({"comments":{"$elemMatch":{"author":"joe","score":{"$gte":5}}}}) //嵌套查询,仅当嵌套的元素是数组时使用,
db.foo.find({"$where":"this.x+this.y==10"}) //复杂的查询,$where当然是非常方便的,但效率低下。对于复杂查询,考虑的顺序应当是正则->MapReduce->$where
db.foo.find({"$where":"function(){returnthis.x+this.y==10;}"}) //$where可以支持javascript函数作为查询条件
db.foo.find().sort({"x":1}).limit(1).skip(10); //返回第(10,11]条,按"x"进行排序;三个limit的顺序是任意的,应该尽量避免skip中使用large-number