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Preface
As we all know, "understanding = heard the name; familiar = know what it is; proficient = used; proficient = doing something wrong". (At the end of the article, there are job-hopping salary increases and benefits)
I believe that everyone is familiar with MySQL indexes. Indexes are data structures that help MySQL obtain data efficiently. Indexes, as a key piece of knowledge in MySQL, appear frequently in interviews.
I think I have a good understanding of MySQL indexing knowledge, and my colleagues also enthusiastically call me a boss in their work. In order to enter Ali, I specially spent about a month reviewing relevant knowledge, and confidently wrote "proficient in MySQL" on my resume. I did not expect to be abused by the Ali interviewer... ( about this interview topic and Organized answers, if you need it, you can click here to get it for free )
In the first half of the conversation, I had a very good conversation with the interviewer. During the chat, I mentioned that our business volume is relatively large. There are about millions of new data generated every day. The interviewer is interested...
Interviewer: Do you store such a large amount of data in relational databases every day?
Me: Yes, we use MySQL database online.
Interviewer: Did you optimize the query?
Me: We used the index.
Ali interview questions
(Due to space issues, I will only list the questions of Ali interviewers in the following content, and I can only answer about half of them)
- Can you talk about why the B+ tree is better than the B tree in query?
- Apart from the above range query, can you tell some other differences?
- We just talked about B+ Tree, do you know what can be stored in the leaf nodes of B+Tree?
- Is there any difference between clustered index and non-clustered index when querying data?
- You just mentioned that the primary key index query will only be checked once, while the non-primary key index needs to be queried multiple times. Is this the case in all cases? Will non-primary key indexes be queried multiple times?
- Joint index, leftmost prefix matching
- What factors do you consider when creating an index? Have you ever used a joint index?
- When you create a joint index, how do you choose the order of multiple fields in the joint index?
- Index push down, query optimization
- Do you know what optimizations have been made to indexes in MySQL 5.6?
- Have you created so many indexes, have they taken effect, or have your SQL statements used index queries, have you made statistics?
- When troubleshooting, is there any way to know if there is an index query?
- So what happens when an index is clearly created, but the index is not passed during execution?
- Oh, let's ask so much about indexing knowledge for now. What is the transaction isolation level of your online data?
For programmers, going to any company for an interview, database is inevitable. The more a developer masters MySQL, the more things you can do.
MySQL query process
- To complete business functions, you must understand basic Sql statements.
- To do performance optimization, you must understand the index and understand the engine.
- To sub-database and sub-table, you must understand the master-slave and the separation of reading and writing.
- To do security, you must understand permissions, understand backups, and understand logs.
- To do a cloud database, you must understand the source code and understand the bottleneck.
Real Interview Questions for Ali (Ant Financial, Cainiao).PDF
Ant Financial, Java Advanced
- In mysql database, under what circumstances are indexes set up but not available?
- Will mysql optimize, mycat sub-database, vertical sub-database, horizontal sub-database?
- Have you understood the storage engine of mysql?
Cainiao network, Java intermediate (message queue, Springcloud, jvm, spring, data structure, database, thread pool)
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