Download SQL> create table student(rollno number(3),name varchar(15

Ex No:1
Date:
DDL(Data Definition Language) Commands
AIM:
To write a query with a function of DDL commands such as create , alter , drop.
PROGRAM:
CREATE TABLE:
This sql command is used to creating a table .
SQL>
create
table
student(rollno
number(3),name
varchar(15),address
varchar(20),phno number(10));
Table created.
SQL> desc student
Name
Null?
-----------------------------------------
Type
-------- ----------------------------
ROLLNO
NUMBER(3)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHNO
NUMBER(10)
ALTER TABLE:
This sql command is used to alter or do any changes in a table .
SQL> alter table student add(age number(2));
Table altered.
Database Management System Lab
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SQL> desc student
Name
Null?
-----------------------------------------
Type
-------- ----------------------------
ROLLNO
NUMBER(3)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHNO
NUMBER(10)
AGE
NUMBER(2)
PRIMARY KEY:
This sql command is used to find a unique value.
SQL> alter table student add(primary key(rollno));
Table altered.
SQL> desc student
Name
Null?
----------------------------------------ROLLNO
--------
NOT NULL
Type
---------------------------NUMBER(3)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHNO
NUMBER(10)
AGE
NUMBER(2)
MODIFY THE DATATYPE:
This sql command is used to modify a table .
SQL> alter table student modify(rollno number(5));
Table altered.
SQL> desc student
Name
Null?
-----------------------------------------
--------
Type
----------------------------
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ROLLNO
NOT NULL NUMBER(5)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHNO
NUMBER(10)
AGE
NUMBER(2)
RENAME COLUMN:
This sql command is used to rename a column in a table .
SQL> alter table student rename column phno to phoneno;
Table altered.
SQL> desc student
Name
Null?
----------------------------------------ROLLNO
Type
-------- ----------------------------
NOT NULL NUMBER(5)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHONENO
NUMBER(10)
AGE
NUMBER(2)
DELETE COLUMN:
This sql command is used to delete a column in a table .
SQL> ALTER TABLE STUDENT DROP(AGE);
Table altered.
SQL> desc student
Name
Null?
-----------------------------------------
--------
Type
----------------------------
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ROLLNO
NOT NULL NUMBER(5)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHONENO
NUMBER(10)
RENAME THE TABLE NAME:
This sql command is used to delete a table name .
SQL> rename student to student1;
Table renamed.
SQL> desc student1
Name
Null?
----------------------------------------ROLLNO
Type
-------- ----------------------------
NOT NULL
NUMBER(5)
NAME
VARCHAR2(15)
ADDRESS
VARCHAR2(20)
PHONENO
NUMBER(10)
SQL> desc student
ERROR:
ORA-04043: object student does not exist
DELETE THE TABLE:
This sql command is used to delete a table .
SQL> drop student1;
Table droped.
SQL> desc student1
ERROR:
ORA-04043: object student1 does not exist
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RESULT
Thus the DDL commands are created,altered and deleted.
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