background:
1. I am a java programmer
2. Recently interviewed for a senior development position
3. The previous project mainly used less oracle,mysql, and the companies interviewed basically used mysql"s
4. I am weak in the database
5. Recently, I have been watching "High performance mysql"
6. Not only the question of the interview, but also want to improve in this respect
-split line-
question:
will ask questions related to database query optimization and database overall optimization in the interview.

my answer in the interview:
1.select use less * and only use the fields that need to be used
2. Try to use as few associated queries as possible, and make data redundancy for some fields appropriately
3. For some of the most commonly used query fields, you can consider using indexes (the interviewer will usually ask what types of indexes there are, the data structure of the index B-tree, index failure, etc.)
4.mysql can use explain, to check the query performance of sql, through key you can see the index used by the query, type can see whether it is a full table scan or index scan, etc., try to make sql query through the index

so I would like to ask you, what are the questions of my answer, from what aspects can I answer, and what can I learn from?