【MongoDB】The high Query operation of MongoDB(一)

In the last blog, we talked about the basic operation of MongoDB, including insert, query, remove and update. Now in this blog, we will further hava a good understanding of  querying operation. 

At first, let‘s create 1000 recors for testing. As the following picture depicts.

Condition Expression 

1. <, <=, >, <=  is correspondent to ‘$lt’,‘$Ite‘, ‘$gt‘ and ‘$gte‘

2. $all

This operation is analogous to the $in operation. But the difference is that $all operation requires every elements in the array to be included in the return result. 

3. $exists

$exists operation check whether one field exists.