Database Management Systems (DBMS) Interview Questions

Checkout Vskills Interview questions with answers in Database Management Systems (DBMS) to prepare for your next job role. The questions are submitted by professionals to help you to prepare for the Interview.
    

Q.1 How do you prioritize tasks?
Tasks also need to be prioritized to accomplish the organizational goals as per the specified KPIs (key performance indicators). Prioritization of tasks is done on the basis of various factors like: the tasks relevance, urgency, cost involved and resource availability.
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Q.2 How do you manage your time?
Time management is of utmost importance and is applied by: using to do lists, being aware of time wasters and optimizing work environment
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Q.3 Why do you want to work in DBMS at this company?
Your company offers me many avenues of growth and enhance my DBMS skills. Your company offers opportunities for future growth in DBMS role. Also considering my education, skills and experience I see myself, more apt for the post.
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Q.4 Why do you want DBMS job?
I want the DBMS job as I am passionate about making companies use DBMS more efficiently by using new technologies and taking stock of present technology portfolio to maximize their utility.
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Q.5 How you manage work under pressure?
I have always been someone who is motivated by deadlines, so I thrive when there is a lot of pressure on me.
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Q.6 Which constraint ensures that all values in a column are different in a DBMS?
UNIQUE constraint ensures that all values in a column are different in a DBMS
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Q.7 What does aggregate functions returns
aggregate functions returns a single value
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Q.8 What is used to write the database schema?
Data Definition Language is used to write the database schema
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Q.9 What is BCNF in a DBMS?
BCMF expands to Boyce-Codd Normal Form and is an advanced version of 3NF.
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Q.10 What is Join in a DBMS?
The Join in a DBMS is used to combine information from two or more relations on the basis of the same or related column.
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Q.11 What are the integrity rules in DBMS?
There are two integrity rules in a DBMS - Entity Integrity which specifies that "Primary key cannot have a NULL value." and Referential Integrity which specifies that "Foreign Key can be either a NULL value or should be the Primary Key value of other relation.
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Q.12 What is Lexical analysis in a DBMS?
Lexical analysis in a DBMS is a process of making words or tokens from a character stream.
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Q.13 Which component of query engine receive commands and transmit results to the user?
The SQL Interface is the component of query engine receive commands and transmit results to the user
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Q.14 What does a scalar subquery returns?
Scalar subquery returns a single value.
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Q.15 Which ACID property ensures that any transaction will bring the database from one valid state to another?
The consistency property of ACID ensures that any transaction will bring the database from one valid state to another
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Q.16 Where does the SQL trigger is stored in?
The SQL trigger is stored in database catalog
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Q.17 Which join will produce rows which combine each row from the first table with each row from the second table?
Cross Join will produce rows which combine each row from the first table with each row from the second table
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Q.18 Which operator is used to search for the presence of a row in a specified table that meets certain criteria?
EXISTS operator is used to search for the presence of a row in a specified table that meets certain criteria
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Q.19 Which clause can be used to constrain the number of rows returned by the SELECT statement?
LIMIT clause can be used to constrain the number of rows returned by the SELECT statement
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Q.20 What does the all possible combinations of rows of a relation in DBMS?
The Cartesian product refers to all possible combinations of rows of a relation in DBMS
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Q.21 What does tuple refers to?
Row in a table of DBMS
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Q.22 What refers to entity set which lacks attributes to form a primary key?
Weak entity set refers to entity set which lacks attributes to form a primary key
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Q.23 What does a relation in a relational model refers to?
Relation in a relational model refers to Table in DBMS
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Q.24 Which constraint uniquely identify each rows/records in a database table
PRIMARY Key constraint uniquely identify each rows/records in a database table
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Q.25 Which DBMS constraint ensures that a column cannot have NULL value
NOT NULL Constraint ensures that a column cannot have NULL value
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Q.26 Which constraint provides a default value for a column when none is specified
DEFAULT Constraint provides a default value for a column when none is specified
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Q.27 What uniquely identify a rows/records in any another database table?
FOREIGN Key uniquely identify a rows/records in any another database table
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Q.28 Which constraint ensures that all values in a column satisfy certain conditions?
CHECK Constraint ensures that all values in a column satisfy certain conditions
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Q.29 Does the order of the rows and columns is immaterial, during normalization
Yes, the order of the rows and columns is immaterial, during normalization.
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Q.30 How you manage conflict in your team?
Conflicts arise due to disagreements amongst the purchase and material management team members and which is managed by focusing on the reason for conflict. If needed we can use conflict management technique like collaborating, forcing, accommodating or compromising as per the situation.
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Q.31 What is a Database Management System (DBMS)?
A DBMS is software that manages databases, providing tools to store, retrieve, update, and manage data efficiently.
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Q.32 What is the purpose of a database in an organization?
Databases store and manage structured data, enabling efficient data retrieval, analysis, and decision-making.
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Q.33 Explain the differences between a database, table, record, and field.
A database contains tables, each table contains records, and records consist of fields (columns) that hold data.
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Q.34 What are the key advantages of using a DBMS?
Advantages include data organization, data integrity, data security, efficient querying, and data sharing among users.
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Q.35 What is a relational database management system (RDBMS)?
An RDBMS is a type of DBMS that organizes data into tables with relationships defined by keys, adhering to the principles of the relational model.
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Q.36 Explain the concept of a primary key in a database table.
A primary key is a unique identifier for each record in a table, ensuring data integrity and providing a way to uniquely identify records.
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Q.37 What is a foreign key, and how is it related to primary keys?
A foreign key is a field in one table that references the primary key in another table, establishing relationships between tables.
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Q.38 Describe the differences between SQL and NoSQL databases.
SQL databases are relational, while NoSQL databases are non-relational. SQL uses structured tables, while NoSQL can be document-oriented, key-value, or others.
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Q.39 What is normalization in the context of database design?
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity by adhering to specific rules.
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Q.40 Explain the ACID properties in the context of database transactions.
ACID stands for Atomicity, Consistency, Isolation, and Durability, representing key properties that ensure reliability and integrity of database transactions.
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Q.41 What is a database index, and why is it important?
A database index is a data structure that improves data retrieval speed by providing a quick lookup mechanism for specific columns or fields in a table.
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Q.42 What is the purpose of SQL (Structured Query Language)?
SQL is a domain-specific language used to communicate with and manipulate relational databases, including tasks like querying, updating, and defining schema.
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Q.43 Differentiate between SQL DDL and SQL DML.
DDL (Data Definition Language) deals with defining and managing database structure, while DML (Data Manipulation Language) deals with data manipulation and querying.
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Q.44 What is a database schema, and how does it relate to tables?
A database schema defines the structure, organization, and relationships of tables, specifying columns, data types, and constraints.
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Q.45 Explain the concept of a database transaction.
A transaction is a sequence of one or more SQL statements that are executed as a single unit of work, ensuring data consistency and integrity.
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Q.46 What is data integrity in a database, and how is it enforced?
Data integrity ensures data accuracy and consistency. It's enforced through constraints, primary keys, foreign keys, and validation rules.
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Q.47 What is a stored procedure, and how does it differ from a function?
A stored procedure is a precompiled set of SQL statements stored in a database, while a function returns a single value and is often used in SQL expressions.
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Q.48 What are triggers in a database, and when are they used?
Triggers are database actions automatically executed when specific events, like insert, update, or delete operations, occur in a table.
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Q.49 Explain the difference between a heap file and an indexed file organization.
A heap file stores records in no specific order, while an indexed file uses an index structure for fast access, typically based on a specific key or attribute.
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Q.50 What is a B-tree index, and how does it work?
A B-tree is a balanced tree structure used in database indexing to allow efficient searching, insertion, and deletion of data while maintaining sorted order.
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Q.51 What is a deadlock in a database, and how can it be resolved?
A deadlock occurs when two or more transactions are waiting for resources held by each other. Deadlocks can be resolved through timeout mechanisms or deadlock detection and resolution algorithms.
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Q.52 Explain the concept of database replication.
Database replication involves creating and maintaining multiple copies of a database in different locations to improve availability and fault tolerance.
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Q.53 What is the purpose of database mirroring?
Database mirroring is a high-availability technique that maintains a synchronized copy (mirror) of a database to ensure failover in case of the primary database's failure.
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Q.54 Describe the differences between primary keys and unique constraints.
Both ensure uniqueness, but primary keys also imply the entity's main identifier, while unique constraints allow NULL values.
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Q.55 How does a database backup differ from a database snapshot?
A database backup is a complete copy of a database at a specific point in time, while a database snapshot is a read-only, point-in-time view of a database.
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Q.56 What is a NoSQL database, and when is it suitable for use?
NoSQL databases are non-relational databases designed for flexibility, scalability, and handling unstructured or semi-structured data. They are suitable for applications with evolving data requirements.
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Q.57 Explain the CAP theorem in the context of distributed databases.
The CAP theorem states that a distributed database can provide at most two out of three guarantees: Consistency, Availability, and Partition Tolerance.
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Q.58 What is sharding in a database, and why is it used?
Sharding involves partitioning a database into smaller, manageable pieces (shards) distributed across multiple servers or nodes to improve scalability and performance.
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Q.59 What is a database index fragmentation, and how can it be addressed?
Index fragmentation occurs when indexes become inefficient due to data changes. It can be addressed by rebuilding or reorganizing indexes.
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Q.60 Explain the purpose of a database view.
A database view is a virtual table derived from one or more underlying tables. It simplifies data access by providing a customized, logical representation of data.
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Q.61 What is the role of the database administrator (DBA)?
The DBA is responsible for managing and maintaining the database system, including tasks like data backup, security, optimization, and user access control.
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Q.62 Describe the differences between horizontal and vertical partitioning.
Horizontal partitioning divides a table into subsets of rows, while vertical partitioning divides a table into subsets of columns.
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Q.63 What is the purpose of data modeling in database design?
Data modeling involves defining the structure, relationships, and constraints of data to create a blueprint for database design and development.
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Q.64 Explain the concept of referential integrity in database design.
Referential integrity ensures that relationships between tables are maintained, preventing actions that would violate the integrity of the data.
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Q.65 What is the difference between a clustered and a non-clustered index?
A clustered index determines the physical order of data rows in a table, while a non-clustered index provides an additional, separate structure for efficient data retrieval.
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Q.66 How can you optimize SQL queries for better database performance?
Query optimization involves using appropriate indexes, minimizing table scans, writing efficient joins, and considering the use of query execution plans.
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Q.67 What are database transactions, and why are they important?
Transactions group a series of database operations into a single, atomic unit. They are essential for maintaining data consistency and integrity.
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Q.68 Explain the concept of database replication lag.
Replication lag is the delay between changes made to a primary database and the time it takes for those changes to be replicated to secondary copies in a distributed environment.
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Q.69 What is a composite key, and when is it used in database design?
A composite key is a key that consists of multiple columns, used when a single column does not provide sufficient uniqueness for identifying records.
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Q.70 What is the purpose of database normalization?
Database normalization eliminates data redundancy, reduces anomalies, and improves data integrity by organizing data into separate related tables.
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Q.71 Explain the differences between a data warehouse and an OLTP database.
Data warehouses are designed for analytical processing, while OLTP databases handle transactional data processing for day-to-day operations.
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Q.72 What is the role of a database index in query optimization?
A database index improves query performance by providing a fast path to locate specific rows in a table, reducing the need for full table scans.
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Q.73 How does a full-text search index differ from a regular database index?
Full-text search indexes are specialized indexes optimized for searching and retrieving text-based data, such as documents or text columns, based on relevance ranking.
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Q.74 What is the purpose of database denormalization?
Database denormalization involves intentionally introducing redundancy into a database to improve query performance, especially for read-heavy workloads.
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Q.75 Explain the concept of a database transaction log.
A transaction log records all changes made to a database, allowing for recovery and rollback of transactions, as well as ensuring data consistency.
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Q.76 What is the role of the SQL JOIN operation in database queries?
SQL JOIN operations combine data from multiple tables based on related columns, allowing retrieval of information from related records.
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Q.77 What is an ETL process, and why is it used in data warehousing?
ETL (Extract, Transform, Load) is a data integration process that extracts data from source systems, transforms it into a suitable format, and loads it into a data warehouse for analysis.
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Q.78 How can you ensure data security in a database system?
Data security measures include authentication, authorization, encryption, access controls, and regular security audits to protect data from unauthorized access and breaches.
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Q.79 Explain the concept of database backup and recovery.
Database backup involves creating copies of the database to safeguard against data loss. Recovery involves restoring the database to a previous state in case of failure.
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Q.80 What is the purpose of database constraints, and how do they enforce data integrity?
Constraints define rules that restrict the type of data that can be stored in a table, ensuring data integrity and adherence to business rules.
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Q.81 What is a self-join in SQL, and when is it useful?
A self-join occurs when a table is joined with itself. It's useful when you need to establish relationships within the same table, often using aliases.
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Q.82 Explain the concept of a database trigger.
A database trigger is a predefined action that automatically executes in response to a specific event, such as an INSERT, UPDATE, or DELETE operation.
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Q.83 What is the difference between a view and a materialized view?
A view is a virtual table that retrieves data dynamically from its source tables, while a materialized view stores precomputed results for faster access.
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Q.84 Describe the purpose of a database constraint CHECK.
The CHECK constraint enforces a condition that data in a column must satisfy. It ensures that values meet specified criteria before insertion or update.
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Q.85 What is database partitioning, and why is it used?
Database partitioning divides large tables into smaller, more manageable pieces, improving query performance and maintenance.
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Q.86 Explain the concept of a database index hint.
An index hint is a query optimization technique where you suggest to the database which index to use for a specific query, overriding the default behavior.
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Q.87 What is a database snapshot isolation level?
Snapshot isolation is a transaction isolation level that allows each transaction to work with a consistent snapshot of data, even if other transactions are in progress.
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Q.88 What is a database synonym, and how is it used?
A synonym is an alternative name for a database object, allowing users to reference objects using different names for ease of use or abstraction.
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Q.89 Explain the concept of a recursive SQL query.
A recursive SQL query is a query that references itself, typically used to work with hierarchical data structures like organizational charts or file systems.
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Q.90 What is a database materialized view log?
A materialized view log is a table used by the database to track changes in the source table, enabling fast refreshes of materialized views.
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Q.91 Describe the differences between a database primary key and a unique key constraint.
Both ensure uniqueness, but a primary key also implies it's the main identifier for the table, while unique key constraints allow NULL values.
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Q.92 How does a database handle concurrent transactions?
Databases use locking, isolation levels, and conflict resolution mechanisms to manage concurrent transactions and ensure data integrity.
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Q.93 What is the purpose of the COMMIT statement in SQL?
The COMMIT statement finalizes a transaction, making all changes made during the transaction permanent and visible to other transactions.
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Q.94 Explain the concept of database table inheritance.
Table inheritance involves creating new tables that inherit attributes and columns from a parent table, often used in object-relational databases.
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Q.95 What is the difference between a database schema and a database instance?
A database schema defines the structure of tables and relationships, while a database instance represents the running database system with its data.
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Q.96 Describe the differences between a heap file and a clustered file organization.
A heap file stores records in no specific order, while a clustered file organization physically orders records based on a specific field or key.
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Q.97 What is a database deadlock, and how can it be resolved?
A deadlock occurs when two or more transactions are waiting for resources held by each other. Deadlocks can be resolved through timeout mechanisms or deadlock detection and resolution algorithms.
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Q.98 What are database roles, and why are they important?
Database roles are named collections of privileges or permissions that simplify access control management, making it easier to grant or revoke permissions for groups of users.
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Q.99 Explain the concept of a composite index in a database.
A composite index consists of multiple columns and can be used to speed up queries involving multiple criteria on those columns.
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Q.100 What is the purpose of the ROLLBACK statement in SQL?
The ROLLBACK statement undoes changes made during a transaction, reverting the database to its state before the transaction began.
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Q.101 What is database connection pooling, and why is it used?
Connection pooling is a technique that maintains a pool of database connections, reducing the overhead of establishing and closing connections for each client request.
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Q.102 Explain the concept of a database cursor.
A cursor is a database object used to retrieve and manipulate data one row at a time, typically within a stored procedure or a program.
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Q.103 What is a database sequence, and why is it used?
A sequence is a database object that generates unique values, often used for generating primary key values automatically.
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Q.104 Describe the concept of ACID transactions and their importance.
ACID transactions ensure that database operations are Atomic, Consistent, Isolated, and Durable, providing reliability and data integrity.
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Q.105 How does database replication contribute to high availability?
Database replication maintains synchronized copies of data in multiple locations, ensuring availability and fault tolerance by allowing failover to standby databases.
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Q.106 What is a database connection string, and what does it contain?
A connection string is a string containing information needed to connect to a database, including the server address, authentication details, and database name.
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Q.107 Explain the concept of a stored database procedure.
A stored procedure is a precompiled set of SQL statements stored in a database and can be executed as a single unit of work. They are often used for data processing or business logic.
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Q.108 What is the purpose of a database trigger?
A database trigger is a predefined action that automatically executes in response to a specific event, such as an INSERT, UPDATE, or DELETE operation.
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Q.109 How does a database handle transaction isolation levels?
Transaction isolation levels control the visibility of data modifications made by concurrent transactions. Levels include Read Uncommitted, Read Committed, Repeatable Read, and Serializable.
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Q.110 Explain the concept of database sharding and its benefits.
Database sharding divides a database into smaller, manageable pieces (shards) distributed across multiple servers to improve scalability and performance.
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