Question: If you find that some SQL execution is slow, how to find out them?
As long as the specified time is exceeded, an exception will occur
Explain keyword can view the efficiency of sql execution
Create index
create index index name on table name (field name)
CREATE unique INDEX id_user_namess on user(NAME)
B+Tree is used as the index structure, and the data field of the leaf node stores the address of the data record