SQL command used to modify attribute values of one or more selected tuples is :

Question

Accepted Answer

The correct option is (2):

The **UPDATE** command is the precise Data Manipulation Language (DML) statement in Structured Query Language (SQL) that is used to alter or revise the existing data stored in a database table. Its function directly corresponds to the question, as it is the only command explicitly designed to *modify attribute values* (column values) for *one or more selected tuples* (rows). A crucial component of the UPDATE command is the WHERE clause, which specifies the condition for which tuples should have their values changed; if the WHERE clause is omitted, the command will modify the specified column's value for *every* row in the table. Therefore, to change an employee's salary or a product's price, UPDATE is the command you must use, adhering to all transactional integrity rules.

The incorrect option is (1):

**MODIFY** is generally not recognized as a standard, standalone SQL command for manipulating the data within rows across most major database systems. While some database systems may use a proprietary command named MODIFY, the universal SQL standard for changing attribute values in tuples is UPDATE. More commonly, the term MODIFY appears as a subcommand within the **ALTER TABLE** Data Definition Language (DDL) statement (e.g., ALTER TABLE MODIFY COLUMN...). In this context, its role is to change the *definition* or *structure* of a column, such as its data type or size, not the data contents themselves, making it fundamentally different from the required operation.

The incorrect option is (3):

The **INSERT** command is a DML statement whose sole purpose is to add *new* rows (tuples) into an existing table. It is used to introduce fresh data records into the database structure, requiring you to specify values for the new record. It is an operation of creation, not modification. It does not possess the functionality to review and change the attribute values of records that are already stored in the table.

The incorrect option is (4):

The **ALTER** command is a Data Definition Language (DDL) command, which means its purpose is to manage the database *schema* or *structure*. ALTER is used to change the fundamental design of a database object, such as adding a new column to a table, dropping an existing one, or renaming a table. It operates at the definition level of the database, not the data level, and therefore cannot be used to modify the actual attribute values contained within the tuples.