The Structured Query Language (SQL) is foundation for all relational database systems. Most of the large-scale databases use the SQL to define all user and administrator interactions. QL is Non-Procedural language . Its allow the user to concentrate on specifying what data is required rather than concentrating on the how to get it.
The DML component of SQL comprises four basic statements:
* SELECT to get rows from tables
* UPDATE to update the rows of tables
* DELETE to remove rows from tables
* INSERT to add new rows to tables

If a organization is big then it is also there that there is multiple option to store data some people are using EXCEL some are using ACCESS and some of they are using SQL SERVER and in some other format also but there a problem is arise that how to merge that data into one format there is diffrent tool are there for doing this funtion. One of product of SQL SERVER-2000 DTS helps in this problem it provides a set of tool from that tool we can customise are database acording to our need DTSRun is a command-prompt utility used to execute existing DTS packages.

We can get modify, Retrieve by single command or statement in SQL but PL/SQL process all SQL statements one at a time. With PL/SQL, an entire block of statements process in a single command line.sql is structured query language ,various queries are used to handle the database in a simplified manner. while pl/sql is procedural language contains various types of variable,functions and procedures and other major diffrence is Sql as the name suggest it is just structured query language wheareas PLSQL is a commbination of Programming language & SQL.

When we done operation on SQL SERVER that is not commited directly to the database. All operation must be logged in to Transaction Log files after that they should be done on to the main database. CheckPoint are the point which alert Sql Server to save all the data to main database if no check point is there then log files get full we can use Checkpoint command to commit all data in the SQL SERVER. When we stop the SQL Server it will take long time because Checkpoint is also fired.

The main difference between UNION ALL statement and UNION is UNION All statement is much faster than UNION,the reason behind this is that because UNION ALL statement does not look for duplicate rows, but on the other hand UNION statement does look for duplicate rows, whether or not they exist.

Cursor plays there row quite nicely but although there are some disadvantage of Cursor .
Because we know cursor doing roundtrip it will make network line busy and also make time consuming methods. First of all select query gernate output and after that cursor goes one by one so roundtrip happen.Another disadvange of cursor are ther are too costly because they require lot of resources and temporary storage so network is quite busy.

In Log Shipping the transactional log file from one server is automatically updated in backup database on the other server and in the case when one server fails the other server will have the same DB and we can use this as the DDR(disaster recovery) plan.