1. What is Druid?
Druid is the best database connection pool in the Java language. Druid can provide powerful monitoring and extended functions.
Transfer from: https://blog.csdn.net/u014008721/article/details/83269040
sql
You can see the execution plan of the sql statement by adding an explain in front of the query statement
where age+10=3 (the index will not work)
age=3+10 will do
In the data structure of B+ numbers, the data are all in the leaf nodes.
If you perform a series of operations, the hardware meets your conditions, and you have done all your optimizations. At the same time, it is found that it may still be slow. This slowness needs to be considered whether our concurrency has become higher.
The development of enterprises is too rapid, and the concurrency has become higher.