Index

• Index Intro : https://www.youtube.com/watch?v=Xk3cgUdoieU
• MySQL Explain : https://www.sitepoint.com/mysql-performance-indexes-explain/

Single Index vs Composite Index

• https://user3141592.medium.com/single-vs-composite-indexes-in-relational-databases-58d0eb045cbe
• https://www.youtube.com/watch?v=xAQga907NVU

Index Type

• https://www.postgresqltutorial.com/postgresql-indexes/postgresql-index-types/

Cluster vs Non-Cluster Index

• Cluster index is like Primary Key
• Non-Cluster index is like unique index, index
• https://www.geeksforgeeks.org/difference-between-clustered-and-non-clustered-index/
• https://www.sqlshack.com/what-is-the-difference-between-clustered-and-non-clustered-indexes-in-sql-server/

Transaction

• Unit of work on database.
• Transaction must be ACID
  • Atomic : All or nothing. If one of command fail, all will fail.
  • Consistency
  • Isolation
  • Durability : The effects of a successfully accomplished transaction are permanently stored in the database.