在上面的执行示例中，我们已经了解到了什么是子查询。那么子查询可以按照查询返回的不同结果，进行一些简单的分类，如下：

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

使用此语法，可判断内表中行是否有满足条件的，无需LOOP判断，省去好多代码。 3. Select 内表 select 内表，可以i对内表使用sql的语法。例如：取内表某一列的最大值，就可以直接MAX，无需排序后，读第一行， 需要append a表 to B表时，但...

类型操作符$type 操作符$type根据类型查询。可取值和JavaScript类型取值相同。number 数值string 字符串，注意s小写object 对象取出所有age里面是数值类型的文档对象db.c1.find({age:{$type:"number"}});可以借助$exis...

将主查询A的数据，放到子查询B中做条件验证，根据验证结果（true或false）来决定主查询的数据是否保留

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The first diff...

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.