Dropping a table

 In this lesson we are going to study about how to drop a table.

• Drop table  removes the table and all its data from the database entirely.

• Drop table is different from deleting all records from the table .

• Deleting all of the records in the table leaves the table including column and constraint information .

• Dropping the table removes the table definition as well as all of its rows.

Syntax:

DROP TABLE Table_name;

   In this syntex drop table is the keyword and the table name specify the name of table to be droped.

Example:  Drop the temp_employees table

drop table temp_employees.

Related article:

• Truncating a table
• Delete data .

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Copying Data

In this lesson we are going to study about how to copy a data from one table to another table.

Syntex:

Insert into Table_name (column1,column2,....,columnN)  Subquery

here insert is a keyword and into specify the table in which we are going to insert the data and Table_name specify the name of the table ,column1,column2,...,columnN is the name of columns.

Example:

Consider a table : departments.

Now we have created a table: dept with same columns.

create table dept
(id number(7),
name varchar2(25)
)

   We can copy the rows in a insert statement.here we are going to insert the data in newly create dept table from the table departments

insert into dept (id,name)
(select department_id as id,department_name as name
from departments)

   In this insert statement we have written a select statement as subquery.In the select statement we have selected the department_id and given the alias name id,and department_name with alias name name.


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