1
What is a Database Management System (DBMS)?
- A
Software for creating and managing databases
- B
Hardware for storing data
- C
A type of database
- D
A programming language
Show AnswerHide Answer
✓ A. Software for creating and managing databases
🗄️ 130+ Questions • Updated 2026
Database Management System
Multiple Choice Questions
Master DBMS with 130+ curated MCQs covering fundamentals, relational model, SQL, normalization, transactions, concurrency, indexing, and more. Perfect for exams, interviews, and placements.
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📝DBMS MCQs(131 questions)
2
Which of the following is not a type of database model?
- A
Hierarchical
- B
Network
- C
Relational
- D
Linear
Show AnswerHide Answer
✓ D. Linear
3
What is the role of a Database Administrator (DBA)?
- A
Manage and maintain database systems
- B
Write application programs
- C
Design user interfaces
- D
Handle network security
Show AnswerHide Answer
✓ A. Manage and maintain database systems
4
Which of the following is a disadvantage of DBMS?
- A
Data redundancy
- B
Data inconsistency
- C
High cost and complexity
- D
Poor security
Show AnswerHide Answer
✓ C. High cost and complexity
5
What is data independence?
- A
Ability to change schema without affecting applications
- B
Ability to store data independently
- C
Ability to access data without a network
- D
Ability to use any database engine
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✓ A. Ability to change schema without affecting applications
6
Which of the following is a popular DBMS?
- A
MySQL
- B
Oracle
- C
PostgreSQL
- D
All of the above
Show AnswerHide Answer
✓ D. All of the above
7
What is a relation in the relational model?
- A
A table with rows and columns
- B
A relationship between two tables
- C
A type of database
- D
A query language
Show AnswerHide Answer
✓ A. A table with rows and columns
8
What is a tuple in the relational model?
- A
A row in a table
- B
A column in a table
- C
A key
- D
A foreign key
Show AnswerHide Answer
✓ A. A row in a table
9
What is an attribute in a relational model?
- A
A column in a table
- B
A row in a table
- C
A primary key
- D
A foreign key
Show AnswerHide Answer
✓ A. A column in a table
10
What is a candidate key?
- A
A minimal set of attributes that uniquely identifies a tuple
- B
A set of foreign keys
- C
A key that is not unique
- D
A key that is used for indexing
Show AnswerHide Answer
✓ A. A minimal set of attributes that uniquely identifies a tuple
11
What is a foreign key?
- A
A key that references a primary key in another table
- B
A key that uniquely identifies a tuple
- C
A key that is not used in any table
- D
A key that is always numeric
Show AnswerHide Answer
✓ A. A key that references a primary key in another table
12
What is the degree of a relation?
- A
The number of attributes
- B
The number of tuples
- C
The number of constraints
- D
The number of foreign keys
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✓ A. The number of attributes
13
What does SQL stand for?
- A
Structured Query Language
- B
Simple Query Language
- C
System Query Language
- D
Standard Query Language
Show AnswerHide Answer
✓ A. Structured Query Language
14
Which SQL command is used to retrieve data from a database?
- A
SELECT
- B
INSERT
- C
UPDATE
- D
DELETE
Show AnswerHide Answer
✓ A. SELECT
15
Which clause is used to filter records in SQL?
- A
WHERE
- B
HAVING
- C
GROUP BY
- D
ORDER BY
Show AnswerHide Answer
✓ A. WHERE
16
What is the difference between WHERE and HAVING?
- A
WHERE filters rows; HAVING filters groups
- B
WHERE filters groups; HAVING filters rows
- C
Both are the same
- D
HAVING is used for joins
Show AnswerHide Answer
✓ A. WHERE filters rows; HAVING filters groups
17
Which SQL function is used to count the number of rows?
- A
COUNT()
- B
SUM()
- C
AVG()
- D
MAX()
Show AnswerHide Answer
✓ A. COUNT()
18
Which join returns all rows from both tables?
- A
INNER JOIN
- B
LEFT JOIN
- C
RIGHT JOIN
- D
FULL OUTER JOIN
Show AnswerHide Answer
✓ D. FULL OUTER JOIN
19
What is the purpose of normalization?
- A
To reduce data redundancy and improve data integrity
- B
To increase data redundancy
- C
To make queries faster
- D
To secure the database
Show AnswerHide Answer
✓ A. To reduce data redundancy and improve data integrity
20
What is 1NF (First Normal Form)?
- A
No multi-valued attributes and all attributes are atomic
- B
No partial dependencies
- C
No transitive dependencies
- D
All tables have a primary key
Show AnswerHide Answer
✓ A. No multi-valued attributes and all attributes are atomic
21
What is 2NF?
- A
1NF + no partial dependencies on composite keys
- B
1NF + no transitive dependencies
- C
1NF + all attributes depend on the whole key
- D
Both A and C
Show AnswerHide Answer
✓ D. Both A and C
22
What is 3NF?
- A
2NF + no transitive dependencies
- B
1NF + no partial dependencies
- C
All tables are in 3NF automatically
- D
No multi-valued dependencies
Show AnswerHide Answer
✓ A. 2NF + no transitive dependencies
23
What is BCNF (Boyce-Codd Normal Form)?
- A
A stricter version of 3NF where every determinant is a candidate key
- B
Same as 3NF
- C
Weaker than 3NF
- D
Not related to normalization
Show AnswerHide Answer
✓ A. A stricter version of 3NF where every determinant is a candidate key
24
What is denormalization?
- A
Adding redundancy to improve query performance
- B
Removing all redundancy
- C
Splitting tables into smaller ones
- D
Combining tables to reduce complexity
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✓ A. Adding redundancy to improve query performance
25
What is a transaction in DBMS?
- A
A logical unit of work that must be executed atomically
- B
A single query
- C
A database backup
- D
A user session
Show AnswerHide Answer
✓ A. A logical unit of work that must be executed atomically
26
What are the ACID properties?
- A
Atomicity, Consistency, Isolation, Durability
- B
Atomicity, Concurrency, Isolation, Durability
- C
Atomicity, Consistency, Integrity, Durability
- D
Atomicity, Consistency, Isolation, Data
Show AnswerHide Answer
✓ A. Atomicity, Consistency, Isolation, Durability
27
What does Atomicity mean in ACID?
- A
Transaction is executed completely or not at all
- B
Transaction maintains database consistency
- C
Transaction is isolated from others
- D
Transaction changes persist after commit
Show AnswerHide Answer
✓ A. Transaction is executed completely or not at all
28
Which isolation level prevents dirty reads?
- A
READ COMMITTED
- B
READ UNCOMMITTED
- C
REPEATABLE READ
- D
SERIALIZABLE
Show AnswerHide Answer
✓ A. READ COMMITTED
29
What is a dirty read?
- A
Reading uncommitted data from another transaction
- B
Reading data that is corrupted
- C
Reading data that does not exist
- D
Reading data with no locks
Show AnswerHide Answer
✓ A. Reading uncommitted data from another transaction
30
What is a savepoint in SQL?
- A
A point within a transaction to which you can roll back
- B
A point where the transaction commits
- C
A backup of the database
- D
A checkpoint for recovery
Show AnswerHide Answer
✓ A. A point within a transaction to which you can roll back
31
What is concurrency control?
- A
Managing simultaneous operations without conflict
- B
Controlling the order of transactions
- C
Ensuring serializability
- D
All of the above
Show AnswerHide Answer
✓ D. All of the above
32
What is a lock in DBMS?
- A
A mechanism to prevent concurrent access conflicts
- B
A type of transaction
- C
A database backup
- D
A SQL function
Show AnswerHide Answer
✓ A. A mechanism to prevent concurrent access conflicts
33
What is a shared lock (S-lock)?
- A
Allows multiple transactions to read but not write
- B
Allows exclusive write access
- C
Allows both read and write
- D
Prevents any access
Show AnswerHide Answer
✓ A. Allows multiple transactions to read but not write
34
What is an exclusive lock (X-lock)?
- A
Allows only one transaction to read and write
- B
Allows multiple transactions to read
- C
Allows no access
- D
Is used for indexing
Show AnswerHide Answer
✓ A. Allows only one transaction to read and write
35
What is a deadlock?
- A
Two or more transactions waiting for each other indefinitely
- B
A transaction that fails
- C
A corrupted database
- D
A lock that cannot be released
Show AnswerHide Answer
✓ A. Two or more transactions waiting for each other indefinitely
36
What is two-phase locking (2PL)?
- A
Protocol that ensures serializability by two phases: growing and shrinking
- B
Protocol that locks all data at once
- C
Protocol that uses no locks
- D
Protocol that only uses shared locks
Show AnswerHide Answer
✓ A. Protocol that ensures serializability by two phases: growing and shrinking
37
What is an index in a database?
- A
A data structure that improves query performance
- B
A key that uniquely identifies a row
- C
A backup of data
- D
A type of constraint
Show AnswerHide Answer
✓ A. A data structure that improves query performance
38
What is the difference between clustered and non-clustered index?
- A
Clustered index defines physical order of data; non-clustered does not
- B
Non-clustered defines physical order; clustered does not
- C
Both are the same
- D
Clustered index is for primary key only
Show AnswerHide Answer
✓ A. Clustered index defines physical order of data; non-clustered does not
39
What is a B-tree index?
- A
A balanced tree structure used for indexing
- B
A binary tree
- C
A hash index
- D
A dense index
Show AnswerHide Answer
✓ A. A balanced tree structure used for indexing
40
What is a hash index?
- A
Uses a hash function to map keys to bucket positions
- B
Uses a tree structure
- C
Is always clustered
- D
Is used for range queries
Show AnswerHide Answer
✓ A. Uses a hash function to map keys to bucket positions
41
What is the disadvantage of indexes?
- A
They take extra storage and slow down updates
- B
They speed up all queries
- C
They are always necessary
- D
They cannot be dropped
Show AnswerHide Answer
✓ A. They take extra storage and slow down updates
42
What is a bitmap index?
- A
Uses bitmaps for low-cardinality columns
- B
Uses a tree structure
- C
Is used for high-cardinality columns
- D
Is not used in modern DBMS
Show AnswerHide Answer
✓ A. Uses bitmaps for low-cardinality columns
43
What is a data file?
- A
A file that stores database records
- B
A file that stores indexes
- C
A file that stores logs
- D
A file that stores metadata
Show AnswerHide Answer
✓ A. A file that stores database records
44
What is a heap file organization?
- A
Records are stored in no particular order
- B
Records are stored in sorted order
- C
Records are stored in a tree structure
- D
Records are stored in hashed order
Show AnswerHide Answer
✓ A. Records are stored in no particular order
45
What is a sequential file organization?
- A
Records are stored in sorted order based on a key
- B
Records are stored randomly
- C
Records are stored in a linked list
- D
Records are stored in a tree
Show AnswerHide Answer
✓ A. Records are stored in sorted order based on a key
46
What is a file pointer?
- A
A reference to a record's location in a file
- B
A type of index
- C
A primary key
- D
A foreign key
Show AnswerHide Answer
✓ A. A reference to a record's location in a file
47
What is record blocking?
- A
Grouping multiple records into a single block for I/O efficiency
- B
Locking records for concurrency
- C
Encrypting records
- D
Compressing records
Show AnswerHide Answer
✓ A. Grouping multiple records into a single block for I/O efficiency
48
What is data dictionary?
- A
A repository of metadata about the database schema
- B
A table of data
- C
An index
- D
A backup
Show AnswerHide Answer
✓ A. A repository of metadata about the database schema
49
What is query processing?
- A
The process of transforming a high-level query into a low-level execution plan
- B
The process of inserting data
- C
The process of deleting data
- D
The process of indexing
Show AnswerHide Answer
✓ A. The process of transforming a high-level query into a low-level execution plan
50
What is query optimization?
- A
Choosing the most efficient execution plan
- B
Rewriting the query
- C
Removing redundant queries
- D
All of the above
Show AnswerHide Answer
✓ D. All of the above
51
What is a query execution plan?
- A
The steps the DBMS takes to execute a query
- B
The SQL code
- C
The result of a query
- D
The indexes used
Show AnswerHide Answer
✓ A. The steps the DBMS takes to execute a query
52
Which of the following is a typical join algorithm?
- A
Nested loop join
- B
Sort-merge join
- C
Hash join
- D
All of the above
Show AnswerHide Answer
✓ D. All of the above
53
What is a selectivity of a predicate?
- A
The fraction of tuples that satisfy the predicate
- B
The number of attributes in the predicate
- C
The complexity of the predicate
- D
The number of operations
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✓ A. The fraction of tuples that satisfy the predicate
54
What is a cost-based optimizer?
- A
Optimizer that estimates cost of execution plans and picks the cheapest
- B
Optimizer that uses rules only
- C
Optimizer that doesn't use statistics
- D
Optimizer that always picks the same plan
Show AnswerHide Answer
✓ A. Optimizer that estimates cost of execution plans and picks the cheapest
55
What is the Entity-Relationship (ER) model?
- A
A conceptual data model for database design
- B
A physical data model
- C
A query language
- D
A type of index
Show AnswerHide Answer
✓ A. A conceptual data model for database design
56
What is an entity in ER model?
- A
A real-world object or concept
- B
A relationship between objects
- C
An attribute
- D
A key
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✓ A. A real-world object or concept
57
What is a relationship in ER model?
- A
An association among entities
- B
An attribute of an entity
- C
A primary key
- D
A foreign key
Show AnswerHide Answer
✓ A. An association among entities
58
What is an attribute in ER model?
- A
A property or characteristic of an entity
- B
A relationship
- C
A key
- D
A table
Show AnswerHide Answer
✓ A. A property or characteristic of an entity
59
What is a weak entity?
- A
An entity that cannot be uniquely identified without a strong entity
- B
An entity with no attributes
- C
An entity that is dependent on another
- D
Both A and C
Show AnswerHide Answer
✓ D. Both A and C
60
What is cardinality in ER model?
- A
The number of entities that participate in a relationship
- B
The number of attributes in an entity
- C
The number of keys
- D
The number of tables
Show AnswerHide Answer
✓ A. The number of entities that participate in a relationship
61
What is a schema in DBMS?
- A
The overall structure of the database
- B
A user of the database
- C
A table in the database
- D
A query
Show AnswerHide Answer
✓ A. The overall structure of the database
62
What is a superkey?
- A
A set of attributes that uniquely identifies a tuple
- B
A minimal candidate key
- C
A foreign key
- D
A composite key
Show AnswerHide Answer
✓ A. A set of attributes that uniquely identifies a tuple
63
Which SQL statement is used to create a table?
- A
CREATE TABLE
- B
ALTER TABLE
- C
DROP TABLE
- D
INSERT TABLE
Show AnswerHide Answer
✓ A. CREATE TABLE
64
What is a functional dependency?
- A
A constraint between two sets of attributes
- B
A foreign key constraint
- C
A primary key constraint
- D
A unique constraint
Show AnswerHide Answer
✓ A. A constraint between two sets of attributes
65
What does Isolation mean in ACID?
- A
Transactions are executed as if they are the only one running
- B
Transactions are atomic
- C
Transactions are durable
- D
Transactions are consistent
Show AnswerHide Answer
✓ A. Transactions are executed as if they are the only one running
66
What is a timestamp ordering protocol?
- A
Asserts serializability by ordering transactions based on timestamps
- B
Uses locks only
- C
Uses two-phase locking
- D
Uses deadlock detection
Show AnswerHide Answer
✓ A. Asserts serializability by ordering transactions based on timestamps
67
What is a dense index?
- A
An index that has an entry for every search key value
- B
An index that has an entry for some search key values
- C
An index that is clustered
- D
An index that is not used
Show AnswerHide Answer
✓ A. An index that has an entry for every search key value
68
What is a log file?
- A
A file that records all changes to the database
- B
A file that stores the actual data
- C
A file that stores indexes
- D
A file that stores metadata
Show AnswerHide Answer
✓ A. A file that records all changes to the database
69
What is a query plan?
- A
A sequence of operations to execute a query
- B
The result of a query
- C
The query itself
- D
The indexes used
Show AnswerHide Answer
✓ A. A sequence of operations to execute a query
70
What is a specialization in ER model?
- A
Subdividing an entity into sub-entities
- B
Combining entities into a super-entity
- C
Adding attributes to an entity
- D
Removing attributes
Show AnswerHide Answer
✓ A. Subdividing an entity into sub-entities
71
Which of the following is a NoSQL database?
- A
MongoDB
- B
MySQL
- C
Oracle
- D
PostgreSQL
Show AnswerHide Answer
✓ A. MongoDB
72
What is the union operation in relational algebra?
- A
Combines two relations with same schema
- B
Selects rows from a relation
- C
Projects columns from a relation
- D
Joins two relations
Show AnswerHide Answer
✓ A. Combines two relations with same schema
73
Which SQL command is used to remove a table from the database?
- A
DROP TABLE
- B
DELETE TABLE
- C
REMOVE TABLE
- D
TRUNCATE TABLE
Show AnswerHide Answer
✓ A. DROP TABLE
74
What is 4NF?
- A
Eliminates multi-valued dependencies
- B
Eliminates transitive dependencies
- C
Eliminates partial dependencies
- D
Eliminates all anomalies
Show AnswerHide Answer
✓ A. Eliminates multi-valued dependencies
75
What is the two-phase commit protocol?
- A
A protocol to ensure atomicity across distributed transactions
- B
A locking protocol
- C
A recovery protocol
- D
A deadlock detection protocol
Show AnswerHide Answer
✓ A. A protocol to ensure atomicity across distributed transactions
76
What is a deadlock prevention technique?
- A
Wait-die
- B
Wound-wait
- C
Both A and B
- D
None
Show AnswerHide Answer
✓ C. Both A and B
77
What is a covering index?
- A
An index that includes all columns needed for a query
- B
An index that covers the table
- C
An index that is always used
- D
An index on a single column
Show AnswerHide Answer
✓ A. An index that includes all columns needed for a query
78
What is a RAID system?
- A
Redundant Array of Independent Disks for performance/reliability
- B
A type of database
- C
A query language
- D
A backup mechanism
Show AnswerHide Answer
✓ A. Redundant Array of Independent Disks for performance/reliability
79
What is the cost of an index scan?
- A
Depends on the number of index entries read
- B
Depends on the number of blocks in the table
- C
Always cheaper than full scan
- D
Never used
Show AnswerHide Answer
✓ A. Depends on the number of index entries read
80
What is a generalization in ER model?
- A
Combining entities into a super-entity
- B
Subdividing an entity
- C
Adding attributes
- D
Removing relationships
Show AnswerHide Answer
✓ A. Combining entities into a super-entity
81
What is the role of the DBMS catalog (data dictionary)?
- A
Stores metadata about the database objects
- B
Stores actual data
- C
Stores logs
- D
Stores indexes
Show AnswerHide Answer
✓ A. Stores metadata about the database objects
82
What is the Cartesian product operation?
- A
Combines every tuple from one relation with every tuple from another
- B
Selects tuples that satisfy a condition
- C
Projects specific columns
- D
Joins based on equality
Show AnswerHide Answer
✓ A. Combines every tuple from one relation with every tuple from another
83
Which clause is used to group rows with the same values?
- A
GROUP BY
- B
ORDER BY
- C
WHERE
- D
HAVING
Show AnswerHide Answer
✓ A. GROUP BY
84
What is a multi-valued dependency?
- A
A dependency where one attribute determines a set of values
- B
A dependency where one attribute determines one value
- C
A functional dependency
- D
A foreign key dependency
Show AnswerHide Answer
✓ A. A dependency where one attribute determines a set of values
85
What is a phantom read?
- A
A transaction sees new rows inserted by another transaction
- B
A transaction reads uncommitted data
- C
A transaction reads data that is later rolled back
- D
A transaction reads data that is corrupted
Show AnswerHide Answer
✓ A. A transaction sees new rows inserted by another transaction
86
What is granularity of locks?
- A
The size of the data item being locked
- B
The number of locks held
- C
The type of lock
- D
The duration of lock
Show AnswerHide Answer
✓ A. The size of the data item being locked
87
What is a secondary index?
- A
An index on a non-primary key column
- B
An index on the primary key
- C
An index that is clustered
- D
An index that is not used
Show AnswerHide Answer
✓ A. An index on a non-primary key column
88
What is a recovery manager?
- A
Component responsible for ensuring durability and recovery
- B
Component for query optimization
- C
Component for indexing
- D
Component for concurrency
Show AnswerHide Answer
✓ A. Component responsible for ensuring durability and recovery
89
What is a full table scan?
- A
Reading all rows of a table
- B
Reading only some rows
- C
Reading using an index
- D
Reading from cache
Show AnswerHide Answer
✓ A. Reading all rows of a table
90
What is an ISA relationship in ER model?
- A
Represents inheritance (superclass-subclass)
- B
Represents association
- C
Represents aggregation
- D
Represents composition
Show AnswerHide Answer
✓ A. Represents inheritance (superclass-subclass)
91
What is the difference between DBMS and RDBMS?
- A
RDBMS is based on the relational model; DBMS may not be
- B
DBMS is relational; RDBMS is not
- C
Both are the same
- D
RDBMS is older
Show AnswerHide Answer
✓ A. RDBMS is based on the relational model; DBMS may not be
92
What is the selection operation in relational algebra?
- A
Selects rows that satisfy a condition
- B
Selects columns
- C
Renames attributes
- D
Combines relations
Show AnswerHide Answer
✓ A. Selects rows that satisfy a condition
93
What is the difference between DELETE and TRUNCATE?
- A
DELETE removes rows one by one; TRUNCATE removes all rows quickly
- B
TRUNCATE removes rows one by one; DELETE removes all rows quickly
- C
Both are same
- D
DELETE is faster
Show AnswerHide Answer
✓ A. DELETE removes rows one by one; TRUNCATE removes all rows quickly
94
What is 5NF?
- A
Decomposes to eliminate join dependencies
- B
Eliminates transitive dependencies
- C
Eliminates partial dependencies
- D
Eliminates multi-valued dependencies
Show AnswerHide Answer
✓ A. Decomposes to eliminate join dependencies
95
What is a serial schedule?
- A
Transactions execute one after another
- B
Transactions execute concurrently
- C
Transactions are interleaved
- D
Transactions are rolled back
Show AnswerHide Answer
✓ A. Transactions execute one after another
96
What is a lock manager?
- A
Subsystem that manages locks
- B
Subsystem that manages transactions
- C
Subsystem that manages logs
- D
Subsystem that manages queries
Show AnswerHide Answer
✓ A. Subsystem that manages locks
97
What is a full-text index?
- A
An index for text search
- B
An index on a numeric column
- C
An index that is clustered
- D
An index for date columns
Show AnswerHide Answer
✓ A. An index for text search
98
What is an extent?
- A
A contiguous block of storage allocated to a table
- B
A type of index
- C
A backup file
- D
A log file
Show AnswerHide Answer
✓ A. A contiguous block of storage allocated to a table
99
What is a materialized view?
- A
A view whose results are stored physically
- B
A virtual view
- C
A temporary table
- D
A query
Show AnswerHide Answer
✓ A. A view whose results are stored physically
100
What is an aggregation in ER model?
- A
Treating a relationship as an entity
- B
Combining entities
- C
Adding attributes
- D
Removing attributes
Show AnswerHide Answer
✓ A. Treating a relationship as an entity
101
What is a distributed database?
- A
A database that is spread across multiple sites
- B
A database with multiple tables
- C
A database with multiple users
- D
A database with replication
Show AnswerHide Answer
✓ A. A database that is spread across multiple sites
102
What is the rename operation in relational algebra?
- A
Renames attributes or relations
- B
Selects rows
- C
Projects columns
- D
Joins relations
Show AnswerHide Answer
✓ A. Renames attributes or relations
103
What is a view in SQL?
- A
A virtual table based on a query
- B
A physical table
- C
An index
- D
A stored procedure
Show AnswerHide Answer
✓ A. A virtual table based on a query
104
What is the purpose of normalization?
- A
To reduce redundancy and avoid update anomalies
- B
To improve query performance
- C
To make the database smaller
- D
To enforce security
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✓ A. To reduce redundancy and avoid update anomalies
105
What is the read-write set of a transaction?
- A
The data items read and written by the transaction
- B
The attributes of the transaction
- C
The operations of the transaction
- D
The locks acquired
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✓ A. The data items read and written by the transaction
106
What is optimistic concurrency control?
- A
Transactions do not lock data; conflicts resolved at commit
- B
Transactions lock data upfront
- C
Transactions use two-phase locking
- D
Transactions are serialized
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✓ A. Transactions do not lock data; conflicts resolved at commit
107
What is a sparse index?
- A
Index with entries for only some search key values
- B
Index with entries for all search key values
- C
Index that is always clustered
- D
Index that is never used
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✓ A. Index with entries for only some search key values
108
What is a checkpoint in database recovery?
- A
A point where the DBMS writes all changes to disk
- B
A point where transactions are committed
- C
A point where locks are released
- D
A point where indexes are rebuilt
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✓ A. A point where the DBMS writes all changes to disk
109
What is a join operation?
- A
Combining rows from two or more tables based on a common column
- B
Selecting rows from a single table
- C
Projecting columns
- D
Sorting rows
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✓ A. Combining rows from two or more tables based on a common column
110
What is a composite attribute?
- A
An attribute that can be divided into smaller sub-parts
- B
An attribute with multiple values
- C
A key
- D
A foreign key
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✓ A. An attribute that can be divided into smaller sub-parts
111
What is a database query?
- A
A request for data from the database
- B
A request to insert data
- C
A request to delete data
- D
All of the above
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✓ D. All of the above
112
What is the projection operation in relational algebra?
- A
Selects specific columns
- B
Selects specific rows
- C
Renames relations
- D
Joins relations
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✓ A. Selects specific columns
113
Which SQL keyword is used to sort results?
- A
ORDER BY
- B
GROUP BY
- C
HAVING
- D
WHERE
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✓ A. ORDER BY
114
What is an update anomaly?
- A
Data inconsistency due to redundancy
- B
Query returning wrong results
- C
Transaction failure
- D
Lost update
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✓ A. Data inconsistency due to redundancy
115
What is a nested transaction?
- A
A transaction within another transaction
- B
Two independent transactions
- C
A long-running transaction
- D
A distributed transaction
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✓ A. A transaction within another transaction
116
What is the purpose of a lock table?
- A
To track which transactions hold which locks
- B
To store data
- C
To store indexes
- D
To store logs
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✓ A. To track which transactions hold which locks
117
What is a B+ tree index?
- A
A B-tree variant where all keys are in leaves
- B
A binary tree
- C
A hash index
- D
A full-text index
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✓ A. A B-tree variant where all keys are in leaves
118
What is a page in database storage?
- A
A fixed-size block of disk storage
- B
A page of a book
- C
A web page
- D
A record
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✓ A. A fixed-size block of disk storage
119
What is a query rewrite?
- A
Transforming the query into a semantically equivalent but more efficient form
- B
Re-executing the query
- C
Cancelling the query
- D
Caching the result
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✓ A. Transforming the query into a semantically equivalent but more efficient form
120
What is a derived attribute?
- A
An attribute that can be computed from other attributes
- B
An attribute with multiple values
- C
A key
- D
A composite attribute
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✓ A. An attribute that can be computed from other attributes
121
What is a data warehouse?
- A
A large repository for historical data used for analysis
- B
A real-time database
- C
A transactional database
- D
A backup
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✓ A. A large repository for historical data used for analysis
122
What is a relational algebra expression?
- A
A query expressed using relational algebra operations
- B
A SQL query
- C
A query plan
- D
A stored procedure
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✓ A. A query expressed using relational algebra operations
123
What is a stored procedure?
- A
A set of SQL statements stored in the database
- B
A view
- C
An index
- D
A trigger
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✓ A. A set of SQL statements stored in the database
124
What is a determinant in functional dependency?
- A
The left side of the dependency
- B
The right side of the dependency
- C
The key
- D
The foreign key
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✓ A. The left side of the dependency
125
What is a commit?
- A
Making transaction changes permanent
- B
Undoing transaction changes
- C
Starting a transaction
- D
Checking transaction consistency
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✓ A. Making transaction changes permanent
126
What is a deadlock detection algorithm?
- A
Algorithm that identifies deadlocks and resolves them
- B
Algorithm that prevents deadlocks
- C
Algorithm that ignores deadlocks
- D
Algorithm that avoids locking
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✓ A. Algorithm that identifies deadlocks and resolves them
127
What is the purpose of indexing?
- A
To speed up data retrieval
- B
To enforce uniqueness
- C
To organize data physically
- D
All of the above
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✓ D. All of the above
128
What is a tablespace?
- A
A logical storage unit containing tables and indexes
- B
A physical file
- C
A data dictionary
- D
A log file
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✓ A. A logical storage unit containing tables and indexes
129
What is a pipeline in query execution?
- A
Passing intermediate results from one operation to another
- B
Writing results to disk
- C
Parallel execution
- D
Caching results
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✓ A. Passing intermediate results from one operation to another
130
What is a multivalued attribute?
- A
An attribute that can have multiple values
- B
An attribute that has a single value
- C
A composite attribute
- D
A derived attribute
Show AnswerHide Answer
✓ A. An attribute that can have multiple values
131
What is the difference between INNER JOIN and OUTER JOIN?
- A
INNER JOIN returns matching rows; OUTER JOIN returns all rows from one table
- B
OUTER JOIN returns matching rows; INNER JOIN returns all rows
- C
Both are same
- D
OUTER JOIN is faster
Show AnswerHide Answer
✓ A. INNER JOIN returns matching rows; OUTER JOIN returns all rows from one table
❓Frequently Asked Questions
What is DBMS and what are its advantages?
DBMS (Database Management System) is software for creating, managing, and administering databases. Advantages include data consistency, reduced redundancy, data security, data independence, and concurrent access control.
What is the difference between DBMS and RDBMS?
RDBMS (Relational Database Management System) is based on the relational model and stores data in tables with rows and columns. It enforces relationships, keys, and constraints. DBMS is a broader term that includes non-relational systems like hierarchical or network databases.
What is normalization and why is it important?
Normalization is the process of organizing data to reduce redundancy and improve integrity. It involves decomposing tables to eliminate anomalies (insert, update, delete). Normalization is important for maintaining a clean, efficient database design.
What are ACID properties?
ACID stands for Atomicity (all or nothing), Consistency (valid state), Isolation (concurrent execution independent), and Durability (persistent after commit). These properties ensure reliable transaction processing.
What is the difference between SQL and NoSQL?
SQL databases are relational, use structured schemas, and support SQL queries. NoSQL databases are non-relational, use flexible schemas, and are suitable for unstructured data. NoSQL includes document stores (MongoDB), key-value stores, wide-column stores, and graph databases.
What are the different types of joins in SQL?
INNER JOIN returns matching rows from both tables. LEFT JOIN returns all rows from left table and matching from right. RIGHT JOIN is vice versa. FULL OUTER JOIN returns all rows from both tables. CROSS JOIN returns the Cartesian product.
What is an index and how does it improve performance?
An index is a data structure (like B-tree or hash) that allows faster retrieval of rows. It speeds up SELECT queries by reducing data scanning, but slows down INSERT/UPDATE/DELETE because indexes must be maintained.
What is a deadlock and how can it be resolved?
A deadlock occurs when two or more transactions are waiting indefinitely for each other to release locks. It can be resolved by prevention (wait-die, wound-wait), detection (using a wait-for graph) and recovery (aborting one transaction).