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The correct ANSWER is (b) False

To elaborate: Writing a where clause under the update STATEMENT enables US to specify a condition for the selection of TUPLES whose values need to be UPDATED.

Right answer is (c) UPDATE

Explanation: To change a value in a tuple without changing the entire values in the tuple, we USE the update STATEMENT. Eg: update EMPLOYEE set SALARY = salary*1.5;

The correct CHOICE is (b) 1

The explanation is: The DELETE command can operate only on one relation. You cannot give commands like delete R1, R2.

The CORRECT CHOICE is (d) Scalar Subqueries

The EXPLANATION is: SQL subqueries that can OCCUR wherever a value is permitted provided the subquery GIVES only one tuple with a single attribute are called Scalar subqueries. Scalar Subqueries can be used in the SQL update statement when they are used under the set clause.

Correct option is (a) True

To explain I would say: SQL ALLOWS the USE of Subqueries inside the from clause. The subquery used in the from clause MUST have in its RESULT the attributes that are SPECIFIED in the select clause.

Right answer is (c) UNIQUE

To elaborate: The unique construct RETURNS true if the argument in the sub-query is void of duplicates. The not NULL construct avoids the specification of null values into the ATTRIBUTE.

Right answer is (b) A sub-query that uses the correlation NAME of an OUTER query

The BEST I can explain: A CORRELATED sub-query is the one that uses the correlation name of an outer query.

The correct answer is (d) EXISTS

Explanation: The exists construct returns TRUE if a given tuple is PRESENT in the SUBQUERY. The not exists construct GIVES true if a given tuple is not present in the subquery.

The correct answer is (a) all

For EXPLANATION: The all comparison CHECKER is used to check “each and EVERY” condition. The “each” and “every” comparison checkers do not exist in SQL.

Correct CHOICE is (b) False

Best explanation: NESTED SUBQUERIES can be used for comparing two different SETS. Set comparison is an IMPORTANT function of the nested sub-queries.

Correct ANSWER is (a) A SUBQUERY is a select-from-where EXPRESSION that is nested within another query

Explanation: A subquery is a select-from-where expression that is nested within another query. Common uses for sub-queries are to perform tests for set membership, MAKE set comparisons etc.

Correct choice is (b) as

For explanation I would SAY: The “as” keyword is used to rename the resulting attribute after the aggregation FUNCTION has been applied. Just like any other renaming operation, the as keyword simplifies the name of the RELATION.

The correct option is (a) True

To ELABORATE: Yes, we can RENAME the RESULTING ATTRIBUTE after the AGGREGATION function has been applied by using a specific keyword.

Right choice is (b) False

The best EXPLANATION: Any attribute which is present in the having clause without being AGGREGATED must be present in the group by clause. OTHERWISE, the QUERY is considered to be ERRONEOUS.

Correct answer is (a) GROUP by

Explanation: We apply the aggregate function to a group of sets of TUPLES using the group by CLAUSE. The group by clause MUST always be used whenever we are willing to apply the aggregate function to a group of sets of tuples.

The correct choice is (a) True

Explanation: SQL does not PERMIT distinct with count(*) but the USE of distinct is ALLOWED with max and min.

The correct choice is (c) total

For explanation I would say: SQL does not INCLUDE total as a BUILT in aggregate function. The AVG is used to find average, MAX is used to find the maximum and the count is used to count the NUMBER of values.

Correct answer is (a) It is USED to check whether a value is in between TWO specified values

The best I can explain: The between PREDICATE in the where clause is used to check whether a value is in between two EXTERNALLY specified values. This clause is used to list out all tuples having a value within a range.

The CORRECT ANSWER is (a) distinct

Easiest explanation: Specifying the distinct clause beside the select clause RETAINS only one copy of identical tuples resulting from the QUERY.

The correct choice is (C) If the VALUE on which it is applied is blank

Explanation: The is NULL PREDICATE succeeds when the value on which it is applied is blank/null.

Correct OPTION is (a) A string of three LETTERS

To EXPLAIN: The string in the question matches with a string having at least three letters. The first three blank SPACES indicate three letters whereas the PERCENTAGE indicates indefinite spaces after that.

The CORRECT choice is (b) as

To explain: The “as” keyword is used to rename a relation in a query. This is used for convenience as long relation names can reduce READABILITY.

Right option is (a) It CONSIDERS only those pairs of tuples that have the same value on those attributes that appear in the schemas of both RELATIONS

To elaborate: The NATURAL join operation considers only those pairs of tuples that have the same value on those attributes that appear in the schemas of both the relations. The natural join operation operates on 2 relations and GIVES a relation as the result.

Right choice is (d) The Cartesian product of both the relations

For explanation I WOULD say: If we SPECIFY multiple relations in the from CLAUSE and do not specify any conditions in the where clause, the default definition GIVEN by the from clause is the Cartesian product of the relations listed in the clause. So it returns all the possible combinations of the tuples of the two relations.

The CORRECT option is (b) from

For explanation: The “from” clause CONTAINS the ATTRIBUTE NAMES on which the “which” clause can be used on.

The correct ANSWER is (a) all

To ELABORATE: The “all” KEYWORD is used beside the select clause to explicitly SPECIFY that duplicates are not removed.

Correct option is (B) alter table R DROP A

The best I can EXPLAIN: We can delete an attribute from a RELATION using the alter table command with the following syntax

alter tabledrop

Right option is (C) DELETE from R

For explanation: The delete from command is used to delete all the TUPLES in a relation. The DROP table totally deletes a relation.

Correct choice is (a) drop table R

Best explanation: The drop table command is USED to delete a RELATION from a database WHEREAS the delete table REMOVES all the TUPLES from a re

Right answer is (d) foreign key(a1, a2)

Explanation: WHENEVER the integrity constraint foreign key is MENTIONED, the attributes that are the foreign KEYS should always be referenced from the RELATION in which they are PRIMARY keys.

Right option is (b) String(n)

To explain I would say: The SQL STANDARD does not SUPPORT String(n) but it supports char, varchar and FLOAT.

The correct option is (B) False

For explanation: If a RELATION has a foreign KEY, then it is CALLED a REFERENCING relation of the foreign key dependency.

The correct answer is (a) Both the statements are true

To elaborate: A tuple is a row is a relation. There can exist multiple FOREIGN KEYS in the same relation because there can exist multiple ATTRIBUTES in the relation that are primary keys in TWO or more other relations.