The difference between redis and mysql

MySQL is a relational database; Redis is a non-relational database.

2. Different roles

Mysql is used to store data permanently to the hard disk, which is powerful but slow.

Redis is used to cache frequently used data, with fast reading speed.

3. Different storage types

Redis stores data in key-value format. The time complexity is O( 1), constant order, while the bottom implementation of MySQL engine is b+ tree, and the time complexity is O(logn), logarithmic order. Redis will be a little faster than MySQL.

Mysql data stores are stored in tables. When searching data, the table should be scanned globally or searched according to the index, which involves disk search. If the search is point by point, the disk search may be faster, but the sequential search will be slower. On the other hand, Redis doesn't have to bother. It is stored in memory itself, and will be fetched directly according to the location of data in memory.