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.
【MongoDB】The high Query operation of MongoDB(一)
原文：http://blog.csdn.net/sxb0841901116/article/details/39456383
