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

Question

Accepted Answer

The correct option is (3):
The **UPDATE** command is the dedicated Data Manipulation Language (DML) statement in Structured Query Language (SQL) used exclusively for changing the existing attribute values of one or more tuples (rows) in a table. It is central to maintaining the correctness of data over time. The command uses a crucial **SET** clause to specify which column's data should be changed and what the new value should be, and a vital **WHERE** clause to precisely select which rows are targeted for modification. By allowing developers to conditionally select and change specific data points, the UPDATE command ensures data accuracy without altering the underlying table structure.

The incorrect option is (1):
The **DROP** command is a Data Definition Language (DDL) statement, meaning its purpose is to manage the structure, not the content, of the database. When executed, DROP permanently deletes an entire object from the database, such as a table, a view, or an index. It does not modify attribute *values*; rather, it destroys the complete table structure and all the tuples it contains, which is a far more severe operation than simple data modification. Therefore, it cannot be used to selectively change a few attribute values.

The incorrect option is (2):
The **ALTER** command is another DDL statement that is used to change the *definition* or *structure* of a table. For example, we use ALTER TABLE to add a new column, drop an existing column, or change the data type of a column. While it modifies the attributes, it changes the *schema* (the column definition) of the table, not the *values* (tuples) stored within that schema. Data values themselves remain unchanged unless an additional operation is performed.

The incorrect option is (4):
The term **Modify** is often used in general language to mean 'change,' but it is not a standard, standalone command in most major SQL dialects (like T-SQL, PostgreSQL, or standard SQL) specifically for changing tuple data. In some dialects, such as MySQL and Oracle, the `MODIFY` keyword is used *within* the **ALTER TABLE** DDL command to change the characteristics of an existing column (e.g., its data type or size), which is a structural change, not a data value change. Therefore, the standard and correct DML command for changing attribute values is always UPDATE.