4 votes 4 votes In a relational database model, NULL values canbe used for all but which one of the following? To allow duplicate tuples in the table by filling the primary key column(s) with NULL To avoid confusion with actual legitimate data values like 0 (zero) or integer columns and " (the empty string) for string columns To leave columns in a tuple marked as "unknown" when the actual value is unknown To fill a column in a tuple when that column does not really "exist" for that particular tuple Databases ugcnetcse-june2016-paper2 rdbms sql databases + – go_editor asked Aug 14, 2016 • recategorized Nov 5, 2017 by Devshree Dubey go_editor 4.8k views answer comment Share Follow See 1 comment See all 1 1 comment reply focus _GATE commented Aug 14, 2016 reply Follow Share c option answer ?? 0 votes 0 votes Please log in or register to add a comment.
Best answer 2 votes 2 votes ans will be A Null values can not be used in primary key (Entity constraint) Sanjay Sharma answered Aug 14, 2016 • selected Oct 9, 2017 by Sankaranarayanan P.N Sanjay Sharma comment Share Follow See all 3 Comments See all 3 3 Comments reply focus _GATE commented Aug 14, 2016 reply Follow Share A option says filling the primary key column(s) with NULL how this is possible???? 0 votes 0 votes Sanjay Sharma commented Aug 14, 2016 reply Follow Share not possible only then it can not be applied to A . rest are applications of NULL 0 votes 0 votes 123neeraj commented Aug 30, 2020 reply Follow Share but i think question is asking for application of null? 0 votes 0 votes Please log in or register to add a comment.