Some Awareness regarding SQL

Hi,
Here are some basic points regarding the SQL.
SQL : Structured Query Lang, which is developed by IBM in 1970's.
It has 4 sub lang.
1) DDL(Data definition lang) : Meta data, like size, type, : create, alter, drop.
2) DML(Data Manipulation lang) select, insert, update, delete.
3) TCL(Transaction control lang) (commit, rollback, save point).
4) DCL(Data Control lang).
RDBMS
RDBMS : It is conceptual accepts , specifies how the data to be persisted... & some rules how to arrange the data so that the retrieval/insertion/processing the logic will be easy.
RDBMS : is the root & we can have so many implementations for RDBMS like Oracle, SQL Server, Sybase....

In General all the RDBMS will follow 4 properties which are called as ACID.
ACID :
1) Atomicity (bunch of statements should execute at a time or rollback)
2) Consistency( All the time the data should maintain some consistency)
3) Isolation( one transaction should not effect the other transaction )
4) Durability. ( No data loss...Achieved using the locks)