Accessing data from Data Warehouse

I am a first year Bsc Student. Although there are five subjects in my upcoming semester, but there is one subject that attracts me the most , it is DBMS or you can call it as database management system. I am looking forward to study that subject and make it thorough from now on because I look myself as a Data Base Administrator. Yes there is a long path to walk ahead , for that I know I should be very strong with my basics, although the semester has not started yet I am thinking to do a bit of study myself , so I had some doubts regarding the data warehouse, can you please explain in brief how it helps in managing and accessing the data stored in it. I would be so glad if you share your ideas with me.

As the name suggests a data warehouse is also a warehouse , but here it does not store grains or eatables , but it is a repository of data been archived in the form of relational data. By relational data I mean in the tabular form where it can be retrieved easily by querying it. In earlier days the data was not stored in organized way, but in the data ware house , it is well organized , planned and tooled easily to meet the functional requirement of any organization and support in decision making

There were various problems connected with this conventional method, mostly the high costs included in data storage. In the presence of legacy systems architecture, a huge amount of redundancy was there which was the biggest hinge for the multiple decision support enterprises. So a process was required that could the process of gather, cleanse off the redundancy and integrate the whole data from various resources, this gave emergence to Data warehousing

Querying the data from the the database is known as Data mining, the most preferable tool to mine a data from a data base is an SQL query. Since we know that the data in a relational data base is stored in a tabular format. Then we can use SQL queries to retrieve data stored from those records. It stands for Structured Query Language and is normally designed to manage the data stored in a relational database. Its basic principal include to insert a data, to update it and to delete it from the data base. The records are being fetched on the basis of rows and columns. Select clause is the most common clause being used , for example if you want to fetch the record of the employee whose salary is more than 15000 then you can use the SELECT statement , in which you will mention the name column and the FROM clause will include the name of the table and the WHERE clause will include the condition
SELECT ename
FROM employee
WHERE salaray>15000

There are four features of a data warehouse, and the first is that the data ware house is subject oriented, it means that the data can be fetched on the base of any particular subject. Suppose if want to know the maximum sale of the month, then you can first lookout for your regular customer. The next feature of a data warehouse is that the data stored in the warehouse is in integrated format. Or you can say it is consistent, any changes made in the architecture does not harm the consistency of the data being stored in it and a data warehouse is non volatile and time variant.