SQL MCQ

Which of the following is not a valid SQL type?

• FLOAT

• NUMERIC

• DECIMAL

• CHAR

Answer explanation

DECIMAL is actually NUMERIC in SQL

Which of the following is not a TABLE command?

• TRUNCATE

• ALTER

• UPDATE

• DELETE

• DROP

Answer explanation

insert, update, delete: data manipulation

create, alter, truncate, delete, drop: table manipulation

Select all the kinds of Views in SQL:

• Simple

• Virtual

• Materialized

• Complex

Answer explanation

-Virtual = not stored in the database; just a query for constructing the

relation

- Materialized = actually constructed and stored

How many primary keys a table can have?

• 1

• 0

• 2

• Depends on no. of Columns

Which of the following is not Constraint in SQL?

• Primary Key

• NOT NULL

• Check

• UNION

Which operator is used to compare a value to a specified list of values?

• ANY

• BETWEEN

• ALL

• IN

Answer explanation

The IN operator easily tests the expression if it matches any value in a specified list of values. It reduces the use of multiple OR conditions.

The WHERE or HAVING clause uses the ANY and ALL operators. ANY gives the result when any subquery value matches the specified condition. The ALL give the result when all subquery values match the specified condition.

The BETWEEN operator selects values only in the given range.

What operator tests column for absence of data?

• NOT Operator

• EXISTS Operator

• IS NULL Operator

• None of the above

Answer explanation

The IS NULL operator is used to testing the empty values in the table's column. It returns true if column values are NULL.

The NOT operator gives the result only when the specified condition is not true.

The EXISTS operator used in combination with a subquery, and if a subquery returns any record, this operator returns true. Otherwise, it will return false.

19) Which of the following is also called an INNER JOIN?

• SELF JOIN

• EQUI JOIN

• NON-EQUI JOIN

• Different answer

Answer explanation

The INNER JOIN returns data from the two or more tables that match the specified condition and hides other records.

EQUI JOIN is similar to INNER JOIN that returns records for equality or matching column(s) values of the relative tables.

NON-EQUI JOIN is returned those records that are not matching in the relative tables.

SELF JOIN returns records from the tables by joining itself

_______ is a constraint that can be defined only at the column level?

• UNIQUE

• NOT NULL

• CHECK

• PRIMARY KEY

Which of the following operator can be used with a multiple-row subquery?

• =

• BETWEEN

• NOT IN

• <>

Answer explanation

The multiple-row subqueries produces multiple rows of results. We can only use the NOT IN operator in SQL can only be used with multiple-row subqueries. And all other operators must be used with single row subquery only. Therefore, BETWEEN, '=', and '<>' operators work with single row subquery.