How do Databases Work? | System Design

This video goes over how databases work internally--specifically how they parse and execute SQL queries in the most efficient way possible.

Table of Contents:
0:00 - Introduction
0:09 - What is a Database
0:37 - Declarative vs Imperative
2:10 - Query Execution Process
2:48 - Parser
3:37 - Query Planner
4:09 - Examples of Query Plans
8:04 - Query Planner Overview
8:37 - Query Execution
8:48 - Conclusion

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🎯 Key points for quick navigation:

00:00 *📚 What is a database and how queries work?*
- Database takes in SQL queries to retrieve data.
- SQL is declarative, focusing on what data is needed not how to get it.
- Internal complexities of a database translate declarative queries into execution steps.
02:09 *🧠 Process of executing a query in a database*
- Database query process involves parsing, query planning, and execution.
- Parser translates SQL query into a data structure for the database to use.
- Query planner optimizes query execution and evaluates different plans based on database characteristics.
03:32 *🔍 Role of parser in database query execution*
- Parser converts raw SQL text into a parse tree for easier database evaluation.
- Parse tree organizes query components like select, from, and where clauses for database use.
- Use of parse tree allows the database to recursively evaluate query components.
08:12 *⚙️ Query planner in optimizing database query execution*
- Query planner considers table statistics, cost constants, and available indexes for query optimization.
- It generates multiple plans, evaluates costs for each, and outputs the most efficient plan.
- Optimizing query planning leads to faster and more efficient database query execution.

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[mohitnagpal]

Your videos are very helpful and to the point.

[Travala]

Thanks, I really like the videos! But (in my personal opinion) it would be much easier to perceive information if you took some pauses when you speak. Otherwise, videos are really helpful! And one of the topics I would love to know more about is how systems like Apache Spark or Hadoop work internally, what are the specific use cases and etc. Thanks again!

[mineline]

dude this laser pointer is giving me flashbacks from school lmao

[congminhluu]

I'm dumb so any help would be appreciated. Why are hash join on 100 rows tables faster than hash join on 10 rows tables ?

[Zmey]

Thank you a lot for your video. Maybe next time tell us about the pros and cons of SQL? For example, that is invented in the 80s and that it is ineffective when working with a large amount of data?

[saramshshrestha]

CS degree help me understand it pretty clearly. 😅