SELECT statement

SELECT statement has five major sections

1. SELECT key word 
2. column specification 
3. from key word
4. table or list of tables
5. where clause


Section 1, 2,3 and 4 are mandatory. 5 is optional. 


Explanation with examples  
Consider the table EMP with below structure

Empno	Name	DOB	Salary
10	Mark	12/31/1970	4000
20	Adam	11/20/1980	4500
30	Gary	02/03/1995	3500
40	Lisa	06/14/1960	6000

1) All records
Suppose user needs to see all records from EMP table. Below statement will pull all records from the table. 
select * from EMP;

Note :- 1) In SQL `*` means all columns. Here table has four columns.
            2) `;` is the terminator for the SQL statement.
            3) SQL is not case sensitive.

2) Selected columns
select empno,salary from EMP;
The above statement fetches all empno and salary columns from EMP table

3)  All records with where condition
select empno,salary from EMP where empno = 10;
 The above statement will fetch a record with empno as value 10

4)  All records using where condition and order by
select empno,salary from EMP where empno > 10 order by salary asc;
 The above statement will fetch all record with empno as value > 10 in a ascending order of salary

Select SQL statement has lot of features, some of them are pretty straight forward and some of them are really complex. Normally SQL cannot be learnt by just reading. You just need to practice SQLs with real examples. For that we need a database installed in an operating system.
Each database will have a client utility to manage SQLs. In Oracle Database supplied with  rwo SQL client utilities, SQL Plus and Oracle SQL Developer. SQL Plus is a command line utility and Oracle SQL Developer is a graphical user interface(GUI)

List of standalone tools available in the market.
1. TOAD - www.quest.com
2. Oracle SQL Developer - www.oracle.com
3. PL/SQL Developer - http://www.allroundautomations.com  
4. Advanced Query Tool(AQT) - www.querytool.com