How Does MySQL Handle Partitions? SQL Interview Questions and Answers
In this short sql tutorial we’ll answer another one of the most frequently asked SQL interview questions related to partitions in MySQL.
The functioning of partitions in MySQL is one of the most frequently asked questions in any SQL interview. Here’s what happens behind the MySQL hood:
1) When SELECT SQL queries are used, the partitioning layer opens and locks partitions, the SQL query optimizer determines if any of the partitions can be pruned, then the partitioning layer forwards the handler API calls to the storage engine that handles the partitions.
2) When INSERT SQL queries are used, the partitioning layer opens and locks partitions, determines which partition should the row belong to, then forwards the row to that partition.
3) When UPDATE SQL queries are used, the partitioning layer opens and locks partitions, figures out which partition contains the row, fetches the row and modifies it, then determines which partition should contain the new row, forwards the row to the new partition with an insertion request, then forwards the deletion request to the original partition.
4) When DELETE SQL queries are used, the partitioning layer opens and locks partitions, determines which partition contains the row, then deletes the row from that partition.
Want to know more about SQL partitions or sql queries in general? Perhaps you’re interested in a mysql tutorial? Let us know!
Here are some of the most frequent sql interview questions and answers:
Q: ACID database vs base: what’s the difference?
A: ACID stands for Atomicity Consistency Isolation and Durability, while BASE stands for Bascially Available, Soft State, Eventually Consistent DBMS.
Basically Available means that NoSQL database management systems ensure availability by replication.
Soft State means that there’s no consistency – developers should enforce it themselves.
Eventually Consistent means that BASE databases don’t enforce consistency, however, it can be achieved.
Q: What multi language database design approach should I take? Which DBMS does this technique work with?
A: We recommend you take the row-based approach to multi language database design. This technique works with MySQL, MariaDB, Percona Server, or any other DBMS.
Q: How to protect against SQL injection?
A: Don’t pass user input into a SQL query. You really don’t need to pass a mysql advanced tutorial to know this – it’s that simple!
Q: What types of SQL indexes exist?
A: There are B-Tree indexes, R-Tree indexes, hash indexes, covering indexes, clustered indexes, multicolumn or composite SQL indexes, and prefix indexes.
Q: What is the most popular type of a mysql index?
A: A B-tree sql index is the most popular type of a mysql index.
Q: What is the file to adjust mysql server configuration?
A: The mysql my.cnf file on Linux or the mysql my.ini file on Windows is what you should look into. If needed, we’ll make a separate mysql tutorial for beginners on how it works. A mysql tutorial covering which storage engine – myisam vs innodb – to choose is available here: https://youtube.com/shorts/MpVWcYsJqn4
Q: Is there a sql full course or any mysql tutorial that would cover mysql storage engines in more detail in all complex aspects?
A: Not that we know of, but if needed, we’ll make a sql course talking about everything: sql basics, sql queries, sql vs nosql, sql for data analysis, etc.
Q: Is there a big data tutorial for those looking to work with big data on mysql server?
A: Yes, it’s available here: https://youtube.com/shorts/GurccdgcjL0
Q: I’ve heard that MyISAM performs row level locking?
A: No, that’s a common misconception.
Q: MyISAM vs InnoDB performance – which one is better and why?
A: InnoDB – all of the features that were available in MyISAM are now available in InnoDB.
Make sure to educate yourself on those SQL interview questions and answers the next time you are about to go to a developer interview!
A SQL query to find 3rd highest salary: https://youtube.com/shorts/8D6ok6CbYXE
A video depicting database slowness reasons and quickly explaining how to overcome database slowness can be found here: https://youtube.com/shorts/beLkSf0_Ms4
We’ve also explained ACID database properties here: https://youtube.com/shorts/Ep8-nqXsCV4
Enjoy!
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