There are four major group of qu

There are four major group of query type: DDL, DML, Retreival, Security

Data Definition Language (DDL): commands allow the user to create, modify, and remove database or a component of a data-base, such as tables, view, constrains, synonyms etc. we will be mostly use these following three keywords.

Create
Alter: alter changes the structure of a table
Drop

Data Manipulation and Transactions (DML): DML is used to add, update or delete data.

INSERT
UPDATE: changes the content of the table
DELETE : empty the table

Another most exiting features of DML is handling transaction. MYSQL has some restriction, where as Oracle and SQL server support extensive and full blown transactions; meaning wait for any pending query before committing any changes in the actual data

COMMIT
ROLLBACK

Retrieval : The main keyword for the data retrieval is SELECT; there are six components that are associated with SELECT.

FROM
WHERE
GROUP BY
HAVING
ORDER BY

There are few main operators that helps SELECT , To retrieve data from RDBMS,

Security :

CREATE USER
ALTER USER
DROP USER

Further the following keywords are used to manage the roles and privileges of the users,

SYSTEM privileges
- It handles non object related actions, CREATE SESSION allwoing to log into the data bases and then have the CREATE TABLE privilege. There are 141 system privileges in Oracle RDBMS
Object privileges: the following two key words are used to privileges mostly
- Grant
- Revoke