This post covers how to use WHERE and DELETE in sub-queries. Useful examples to refer to quickly.
Useful string functions for smart SQL developers to write better queries. Useful to read now.
SQL Order of execution is sequence of steps. The database executes each Query in a particular order. Read more.
SQL ALTER statement you can use to add columns to existing TABLE in RDBMS. Not only TABLE you can read all database object where you can use ALTER.