One: Concept:
A Redis instance can include multiple databases, and the client can specify which database to connect to a redis instance, just like creating multiple databases in a mysql, and the client specifies which database to connect to when connecting.
A Redis instance can provide up to 16 databases, with subscripts ranging from 0 to 15. The client connects to database No. 0 by default . You can also select which database to connect to, as follows to connect to database No. 1:
Connect to database 0:
Move the key of the current library to library 1: move newkey 1
