Oracle Basics

Here Are Some Of The Most Popular yet used Oracle statements :



* Types Of Statements : DML - DDL - DCL .



* Types Of Priviliges : System Priviliges , Object Priviliges .



* Types Of Data : Table - View - Index - Sequence .... ( those are the most important ) .



* Types Of Joins : Equi-Join (Inner-Join) , Outer-Join ( Right Outer-Join , Left Outer-Join) , Self-Join , Non-Equi-Join , Cross-Join .



* SubQuery : Used to Define A Variable BASED On UNKNOWN CONDITION(s) .



EX:



SELECT * FROM EMPLOYEES
WHERE DEPARTMENT_ID = ( SELECT DEPARTMENT_ID FROM EMPLOYEES WHERE LAST_NAME LIKE 'Abel' ;



The Subquery used after (=) mark to define the variable Department_id based on unknown condition ( DEPARTMENT_ID FROM EMPLOYEES WHERE LAST_NAME LIKE 'Abel' )



* SAVEPOINT : saved checkpoint which you can roll back your changes to . roll back all user changes to this point.


Index : Schema Object , Used by Oracle Server to Make Retrieval of rows easier .

* Advantages Of VIEWS :

1- Restrict Data Access .

2- Made Complex Queries Easier .

3- Provide Data Independence .

4- Increase Performance .

5- Can be made Read Only , may have Check Option (check constraint).