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Question 3Asked in DSSSB TGT Computer Science (Technical), 12 Sep 2025, Shift 1 (9:00 AM)

Which of the following SQL expressions evaluates to TRUE, according to SQL-99?

  1. ANULL <= NULL returns UNKNOWN
  2. BNULL >= NULL returns UNKNOWN
  3. CNULL IS NULL returns FALSE
  4. DNULL IS NULL returns TRUE
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Correct answer: (D) NULL IS NULL returns TRUE

Explanation

Any ordinary comparison involving NULL (=, <=, >= etc.) gives UNKNOWN, not TRUE. The IS NULL predicate is the special test for nulls, so NULL IS NULL is TRUE.

From DSSSB TGT Computer Science PYQ (Technical), 12 Sep 2025, Shift 1 (9:00 AM)

This is question 3 of DSSSB TGT Computer Science PYQ (Technical), 12 Sep 2025, Shift 1 (9:00 AM). See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.