Question

ANSI-standard SQL allows the use of special operators in conjunction with the WHERE clause. A special operator used to check whether an attribute value is null is (a) BETWEEN (b) IS NULL (c) LIKE (d) IN This question was addressed to me in an international level competition. Asked question is from Multiversion Schemes topic in chapter Concurrency Control of Database Management

Answer 1

Right option is (b) IS NULL The best I can explain: Exists is used to check whether an attribute value is null or not in conjunction with the where clause.