Create,Alter,Modify

 Syntax:

CREATE TABLE table_name
( column1 datatype null/not null,
  column2 datatype null/not null,
  ...
);

  Example

        

CREATE TABLE EMPLOYEE_DETAILS(EMPNAME VARCHAR2(20),EMPAGE INT,EMPSALARY NUMERIC(6,2),EMPDESIGNATION VARCHAR2(20))

OutPut

         

   

                  We can edit the structure of a table by using a keyword 'ALTER'.

                  

Renaming a table

 syntax :

 

  ALTER TABLE table_name
  RENAME TO new_table_name;

 example:

ALTER TABLE suppliers
 RENAME TO vendors;

This will rename the suppliers table to vendors.

Adding column(s) to a table

Syntax :

      To add a column to an existing table, the ALTER TABLE syntax is:

ALTER TABLE table_name
 ADD column_name column-definition;

 example:

ALTER TABLE supplier
 ADD supplier_name  varchar2(50);

    This will add a column called supplier_name to the supplier table.

Modifying column(s) in a table

Syntax :

     To modify a column in an existing table, the ALTER TABLE syntax is:

ALTER TABLE table_name
 MODIFY column_name column_type;

 example:

ALTER TABLE supplier
 MODIFY supplier_name   varchar2(100)     not null;

This will modify the column called supplier_name to be a data type of varchar2(100) and force the column to not allow null values.

                              We can drop particular fields from the table.

Drop column(s) in a table

Syntax :

  

      To drop a column in an existing table, the ALTER TABLE syntax is:

ALTER TABLE table_name
 DROP COLUMN column_name;

 example:

ALTER TABLE supplier
 DROP COLUMN supplier_name;

This will drop the column called supplier_name from the table called supplier.