Which of the following SQL queries is used to retrieve rows from the "customers"table where the "email" column contains NULL values?a. SELECT * FROM customers WHERE email = NULL;b. SELECT * FROM customers WHERE email IS NOT NULL;c. SELECT * FROM customers WHERE ISNULL(email);d. SELECT * FROM customers WHERE email IS NULL;

Which of the following SQL statement(s) return an error (s)?SELECT NULL FROM Customer;SELECT NAME FROM Customer WHERE SALARY = NULL;SELECT NAME FROM Customer;SELECT ALL FROM Customer WHERE SALARY = NULL;SELECT NAME,NIC FROM Customer;

Which of the following statements is TRUE regarding the application of WHERE clause? Can only be used on columns that are present in SELECT clauseIs used to choose the columns that need to be fetched in the resultCan be used on all columnsNone of the above

correct answerWhat is the SQL keyword used to specify that a column can contain NULL values?OptionsNOT NULLNULL ABLEALLOW NULLWITH NULLS

In which cases would you use an outer join?Select one:a.The tables being joined have NOT NULL columns.b.The tables being joined have both matched and unmatched data.c.Only when the tables have a primary key/foreign key relationship.d.The tables being joined have only matched data.e.The tables being joined have only unmatched data.

SELECT, FROM and WHERE are mandatory for any SELECT statement in SQL.