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Rename Attributes
To rename an attribute of an existing table, we use the ALTER TABLE statement with the CHANGE keyword. The
syntax of the ALTER TABLE CHANGE statement is as follows:
ALTER TABLE table_name CHANGE old_name new_name;
For example, to modify the definition of an existing attribute Pin_Code in the EMPLOYEE table, to PinCode,
we execute the statement:
ALTER TABLE EMPLOYEE CHANGE Pin_Code PinCode CHAR(6);
Next, we examine the modified table EMPLOYEE, by executing the following statement:
DESC EMPLOYEE;
On executing the above statement, we get the result as given in Table 11.6d:
Field Type Null Key Default Extra
ID char(5) NO PRI NULL
FName varchar(20) NO NULL
LName varchar(20) NO NULL
Gender char(1) NO NULL
Address varchar(30) YES NULL
City varchar(20) YES NULL
Pin_Code char(6) YES NULL
DOB date YES NULL
Salary int(11) NO NULL
Dept_No int(11) YES NULL
Table 11.6d: Structure of EMPLOYEE table after renaming Pin_Code to PinCode.
4.4.8 UPDATE-SET statement
Suppose the salary of an employee having ID value 10003 has been revised recently. SQL provides an UPDATE
statement for making changes in the tuples already stored in a table. The syntax of the update statement is as follows:
UPDATE table_name
SET Attribute_name = value
[WHERE criterion_for_selecting_specific_tuple];
The following UPDATE statement finds a tuple in the EMPLOYEE table having an ID equal to 10003 and sets the
value of its Salary attribute to 90000.
UPDATE EMPLOYEE
SET Salary = 90000
WHERE ID = '10003';
On executing the above statement, SQL will update the EMPLOYEE tuple for the employee whose ID is 10003
(see Table 4.4).
ID FName LName Gender Address City Pin_Code DOB Salary Dept_No
10003 Muskan Taneja F 8/33, Geeta Colony Delhi 110031 1990-01-25 90000 2
Table 4.4: Result of UPDATE statement on EMPLOYEE table
Database Query using SQL 147

