1. List the capabilities of SQL SELECT statements
2. Execute a basic SELECT statement
3. Describe the use and benefitsof PL/SQL
4. Differentiate between SQL statements and SQL*Plus commands

  SQL statements are very useful and versatile. We can use
  very simple sql statements to frame very simple queries to very
  complex one.

  The efficiency of a database depends on not how many server's or
  how good a hardware it is running on but on the developer's and
  the people accessing the database.

  A efficient coding style should be followed by all the developers.

  A simple sql statement would be of the form:
  select sysdate from dual;
  This is a simple statement which gets the sysdate from the database.

  A little more complex query would be :
 
 select empno from emp group by empno having count(*) > 1 ;
 
  The above query groups the emp table based on the empno
  then we place a filtering condition on the table by the
  having clause to select only those rows which have more than
  one empno.

  A little more complex sql statement would be:
 
 select dept.deptno, deptname from emp , dept
 where emp.deptno=dept.deptno(+) ;
 
  The (+) here is called a outer join.
  The functionality of a outer join is to supply NULL for that
  column value which did not have a corresponding value in the table
  dept.
  Don't worry we will be covering all of these in the coming days.

  sql can also be used to execute many a functions such as :
  chr,ascii, substr, ltrim, rtrim and many more which will
  be covered in detail.

  Here is the basic select statement from above:
 
 select empno from emp group by empno having count(*) > 1 ;
 

  One Line : It is very useful.

  Basically sql statements fall under 3 categories:
  1.)DML ==> Data Manipulation language such as select, delete, Insert.
  2.)TCL ==> Transaction control language such as rollback, commit.
  3.)DDL ==> Data Defining language statements.

  SQL*PLUS
  commands however are executed with in the sql*plus environment
  most of the sql*plus commands have more or less to do with the buffer
  the file which oracle uses as a scratch pad.

  

    Caution:In a sql*plus environment if we issue a statement
    DEL 1
    is this a sql*plus command or statement ?
    A del is used by sql*plus statement to manage the buffer( afiedt.buf)
    if you specify a del 1 it will delete the current sql*plus buffer line
    however if you give  a delete command then oracle will try to delete a table
    value by default.