Explanation:
This UPDATE statement is correct to receive desired results. Correct syntax is UPDATE table_name SET column_name1 = value, column_name2 = value2. You can also use the DEFAULT keyword to set a column value to its specified default value in update statements as well.
Incorrect Answers:
1: You cannot use syntax like UPDATE table_name SET column_name1 = value AND column_name2 = value2. Correct syntax is UPDATE table_name SET column_name1 = value, column_name2 = value2.
2: You cannot use syntax like UPDATE table_name SET column_name1 = value AND column_name2 = value2. Correct syntax is UPDATE table_name SET column_name1 = value, column_name2 = value2.
4: Group function is not allowed to use in the SET clause of the UPDATE command.
5: You cannot set column to value DEFAULT OR NULL: this is wrong syntax to use.
OCP Introduction to Oracle 9i: SQL Exam Guide, Jason Couchman, p. 267-270
Chapter 6: Manipulating Oracle Data

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