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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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DBMS → Introduction to DBMS 3

Which one of the following attribute can be taken as a primary key?
id
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Which of the following statements contains an error?
select empid where empid = 1009 and lastname = ‘geller’;
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SQL applies predicates in the                 clause after groups have been formed, so aggregate functions may be used.
with
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DBMS → Database Architecture 3

Which one of the following cannot be taken as a primary key?
street
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In SQL the spaces at the end of the string are removed by                function.
trim
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The                  keyword is used to access attributes of preceding tables or subqueries in the from clause.
lateral
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DBMS → Data Models 3

An attribute in a relation is a foreign key if the                key from one relation is used as an attribute in that relation.
primary
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The union operation is represented by
u
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Which of the following creates a temporary relation for the query on which it is defined?
with
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DBMS → ER Model 3

The relation with the attribute which is the primary key is referenced in another relation. The relation which has the attribute as a primary key is called                              
referenced relation
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The intersection operator is used to get the            tuples.
common
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Subqueries cannot:
join tables
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DBMS → Relational Model 2

The              is the one in which the primary key of one relation is used as a normal attribute in another relation.
referenced relation
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If we want to retain all duplicates, we must write                  in place of union.
union all
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DBMS → Normalization 2

A                    integrity constraint requires that the values appearing in specified attributes of any tuple in the referencing relation also appear in specified attributes of at least one tuple in the referenced relation.
referential
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The number of attributes in relation is called as its
degree
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DBMS → Functional Dependency 2

The           operation allows the combining of two relations by merging pairs of tuples, one from each relation, into a single tuple.
join
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           clause is an additional filter that is applied to the result.
having
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DBMS → SQL Basics 2

The result which operation contains all pairs of tuples from the two relations, regardless of whether their attribute values match.
cartesian product
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                   joins are SQL server default
inner
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DBMS → DDL Commands 2

The               operation performs a set union of two “similarly structured” tables
union
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The                            is essentially used to search for patterns in target string.
like predicate
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DBMS → DML Commands 2

The most commonly used operation in relational algebra for projecting a set of tuple from a relation is
select
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A            indicates an absent value that may exist but be unknown or that may not exist at all.
null value
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DBMS → Joins 2

The                operator takes the results of two queries and returns only rows that appear in both result sets.
intersect
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If the attribute phone number is included in the relation all the values need not be entered into the phone number column. This type of entry is given as
null
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DBMS → Views 2

A                  is a pictorial depiction of the schema of a database that shows the relations in the database, their attributes, and primary keys and foreign keys.
schema diagram
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The predicate in a where clause can involve Boolean operations such as and. The result of true and unknown is               false and unknown is            while unknown and unknown is            
unknown, false, unknown
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DBMS → Indexes 2

The                    provides a set of operations that take one or more relations as input and return a relation as an output.
relational algebra
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Using the              clause retains only one copy of such identical tuples.
distinct
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DBMS → Transactions 2

Which one of the following provides the ability to query information from the database and to insert tuples into, delete tuples from, and modify tuples in the database?
dml(data manipulation langauge)
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The result of           unknown is unknown.
not
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DBMS → Concurrency Control 2

To remove a relation from an SQL database, we use the              command.
drop table
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Aggregate functions are functions that take a                        as input and return a single value.
collection of values
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DBMS → Deadlock 2

Updates that violate                      are disallowed.
integrity constraints
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A Boolean data type that can take values true, false, and                 
unknown
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DBMS → Database Security 2

The              clause allows us to select only those rows in the result relation of the           clause that satisfy a specified predicate.
where, from
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The          connective tests for set membership, where the set is a collection of values produced by a select clause. The           connective tests for the absence of set membership.
in, not in
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DBMS → PL/SQL 2

The                  clause is used to list the attributes desired in the result of a query.
select
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The phrase “greater than at least one” is represented in SQL by            
> some
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