[MongoDB] The high Query operation of MongoDB (1), mongodboperation

[MongoDB] The high Query operation of MongoDB (1), mongodboperation

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 encoded in the return result.

3. $ exists

$ Exists operation check whether one field exists.

MongoDB cannot start the port and is always waiting for listening

The prompt waiting for connections... indicates that your mongodb has been started.
Do not close this window. Start another command line and use the mongo command to access the database.

[MongoDB] how to stop a MongoDB Server

If the server runs on the terminal as a foreground process, press Ctrl-C. Otherwise, use the kill command to send a signal. If the PID of mongod is 10014, you can use kill-2 10014 (SIGINT) or kill 10014 (SIGTERM ).
When mongod receives the SIGINT or SIGTERM, it exits. That is to say, it will wait until the current operation or file pre-distribution is completed (it takes some time), close all open connections, refresh the cached data to the disk, and finally stop. Do not send SIGKILL (kill-9) to a running MongoDB instance ). This will cause the database to be shut down directly, and the previous steps will be ignored, which will damage the data file.