Foreword:
As we all know, "understand = heard the name; familiar = know what it is; proficient = used; proficient = done something".
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... Sorted out answers, students in need can collect them at the end of the article by themselves)
In the first half of the conversation, I had a great 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 a difference between clustered index and non-clustered index when querying data?
- You just mentioned that the primary key index query can only be checked once, while the non-primary key index needs to be queried multiple times. Is this all the case? 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?
- Under what circumstances will it happen that 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.
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.
The real interview questions of Ali (Ant Financial, Cainiao).PDF
This article is shared with friends who need to interview and brush up questions, and I wish you all the best to get the offer you want. This information mainly includes Java basics, data structures, jvm, multithreading, etc. Due to limited space, only a small part is shown below. Interview questions, friends who need the full version can click a link to jump to receive, link: click here to download for free, get code: CSDN
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 ever understood the storage engine of mysql?
Cainiao network, Java intermediate (message queue, Springcloud, jvm, spring, data structure, database, thread pool)
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