SQL Interview Questions and Answers: SQL Subqueries

In this mysql tutorial we'll answer one of the most frequent SQL interview questions. The question sounds like this: what are sql subqueries?

The answer to these kinds of sql interview questions is as follows: a subquery in sql is any sql query that is inside a CRUD statement or inside of another subquery in mysql or any other database management system.

That's it!

Do you want us to make a sql subquery tutorial with examples? Tell us in the comment section below!

Here are some mysql faqs with answers should you ever need those sql interview questions and answers for your next sql interview:

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?

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?

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.

Q: I want to switch MyISAM to InnoDB - what sql query should I use? Is there a sql tutorial that would help me with this?
A: Use this query - it will give you a list of MyISAM-based tables with a SQL query that you can copy-paste to update all of your MyISAM-based tables to InnoDB (replace "sql tutorial for beginners" with your database name):

We've also made other videos about database performance issues, database performance tuning, and database performance testing.

If you want to learn more about SQL injection, how can impact your applications and how to protect yourself consider subscribing, and until next time.

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