# SQL

1. (very good) [DDL, DQL, DML, DCL and TCL](https://www.geeksforgeeks.org/sql-ddl-dql-dml-dcl-tcl-commands/) - by geek for geeks
   1. DDL – Data Definition Language (create, drop, alter, truncate)
   2. DQl – Data Query Language (select)
   3. DML – Data Manipulation Language (update, insert, delete, lock)
   4. DCL – Data Control Language (grant, revoke)
   5. TCL - Transaction Control Language (commit, rollback, savepoint, set transaction)
2. [Introduction, index, keys, joins, aliases etc.](https://www.youtube.com/watch?v=nWeW3sCmD2k), [newer](https://www.youtube.com/watch?v=9ylj9NR0Lcg)
3. [Sql cheat sheet](https://gist.github.com/bradtraversy/c831baaad44343cc945e76c2e30927b3)
4. [Primary key](https://www.eukhost.com/blog/webhosting/whats-the-purpose-use-primary-foreign-keys/)
5. [Foreign key, a key constraint that is included in the primary key allowed values](https://www.1keydata.com/sql/sql-foreign-key.html)
6. [Index, i.e., book index for fast reading](https://www.tutorialspoint.com/sql/sql-indexes.htm)
7. [Sharding vs Partioning](https://planetscale.com/learn/articles/sharding-vs-partitioning-whats-the-difference)