Question { 2156 }

Describe the Process of Connecting a Database to a Data Analysis Tool.

Answer

The following procedures are often involved in connecting a database to a data analysis tool:

Select the Source of the Data: Choose the database type (such as MySQL, PostgreSQL, or SQL Server) that you wish to connect to.
Install the required drivers: To connect to the database, make sure the data analysis tool has the appropriate drivers.

Configure the Connection: Enter the connection information, including the username, password, port number, database name, and database server address.
Check the Connection: Make sure the tool can connect to the database and that the connection settings are accurate.
Load Data: Use the tool to import or query the data for analysis.
Analyze Data: Make use of the tool's capabilities to analyze data, produce reports, and create visualizations.

Question { 2163 }

How to Optimize Database Queries for Performance?

Answer

Several tactics are used to optimize database queries:

Indexing: To expedite data retrieval, create indexes on columns that are commonly used in WHERE, JOIN, and ORDER BY clauses.
Staying away from Choose: To cut down on the quantity of data processed, only choose the columns you require.
Query Refactoring: To improve efficiency, rewrite complicated queries by leveraging joins effectively or dividing them into smaller subqueries.
Examining Execution Strategies: Utilize tools to identify bottlenecks and evaluate and comprehend the query execution plan.
Setting up a database: Make that the database has enough memory and CPU and is configured correctly.
Archiving Old Data: To keep tables tidy, periodically archive or remove outdated, unnecessary data.

Question { 2163 }

What are Stored Procedures and When would we Use Them?

Answer

Precompiled sets of SQL statements that are kept in the database are called stored procedures. They

Encapsulate business logic and intricate SQL queries.
Reduce network traffic (client-server round trips) to boost performance.
By using parameterized queries to limit access to data, you may improve security.
Make sure it is reusable and consistent across many applications.
When carrying out repetitive operations like data validation, business rule enforcement, or batch processing, stored procedures are especially helpful.

Question { 2013 }

How to Handle Missing Data in a Database?

Answer

One way to deal with missing data in a database is to:

Ignoring: During analysis, ignoring rows with missing values.
Imputing is the process of substituting a default value, mean, median, or value obtained from additional data for missing variables.
Elimination: Taking out rows or columns that contain a significant number of missing values.
Using Placeholders: Using a particular placeholder to indicate missing values

Question { 950 }

Describe the Process of Feature Engineering using SQL.

Answer

To enhance the functionality of machine learning models, feature engineering entails developing new features or altering preexisting ones. Making use of SQL

Creating summary characteristics like total, average, and count is known as aggregation.
Transformations: Changing existing features via mathematical transformations (square root, logarithm, etc.).
Sorting continuous variables into bins is known as bin/group data.
Date Features: Partitioning dates (day, month, and year).

Question { 1136 }

What are the different types of databases?

Answer

• Relational Database (RDBMS) – SQL-based (e.g., MySQL, PostgreSQL, Oracle)
• NoSQL Database – Non-relational (e.g., MongoDB, Cassandra, Redis)
• NewSQL Database – Combines SQL and NoSQL features
• In-Memory Database – Uses RAM for storage (e.g., Redis, Memcached)
• Graph Database – Stores data as nodes and edges (e.g., Neo4j)

Question { 2282 }

What are ACID properties in databases?

Answer

ACID stands for:
• Atomicity – Transactions are all-or-nothing.
• Consistency – Ensures database integrity before and after a transaction.
• Isolation – Ensures transactions don’t interfere with each other.
• Durability – Changes are permanent after a transaction is committed.

Question { 1121 }

What is the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN?

Answer

• INNER JOIN: Returns only matching rows from both tables.
• LEFT JOIN: Returns all rows from the left table and matching rows from the right.
• RIGHT JOIN: Returns all rows from the right table and matching rows from the left.
• FULL JOIN: Returns all rows from both tables, filling in missing values with NULLs.

Question { 1010 }

What is indexing, and how does it improve performance?

Answer

Indexing creates a data structure that speeds up data retrieval operations. It reduces the number of disk accesses required for queries. However, too many indexes can slow down INSERT, UPDATE, and DELETE operations.

Question { 2525 }

What is a deadlock in SQL? How can you prevent it?

Answer

A deadlock occurs when two or more transactions hold locks that the other needs, causing them to wait indefinitely.
Ways to prevent deadlocks:
• Use consistent lock ordering.
• Keep transactions short and fast.
• Use lower isolation levels when possible.
• Implement deadlock detection mechanisms.

Question { 1027 }

What is the CAP theorem?

Answer

The CAP theorem states that a distributed database can achieve at most two of the following three properties:
• Consistency (C) – All nodes have the same data at the same time.
• Availability (A) – System continues to function even if nodes fail.
• Partition Tolerance (P) – System continues to operate despite network failures.
No system can provide all three simultaneously.

Question { 2551 }

How would you optimize a slow SQL query?

Answer

• Use EXPLAIN PLAN to analyze query performance.
• Add indexes where needed.
• Avoid using SELECT *; instead, select specific columns.
• Use proper JOINs and avoid unnecessary computations.
• Optimize queries using caching and denormalization if necessary.

Question { 993 }

How do you handle duplicate records in a database?

Answer

• Use DISTINCT in queries to filter duplicates.
• Use ROW_NUMBER() to identify duplicates:
DELETE FROM Employees
WHERE id NOT IN (
SELECT MIN(id)
FROM Employees
GROUP BY name, email
);
• Implement unique constraints on key fields.

Question { 992 }

How would you design a database for an e-commerce website?

Answer

• Tables Needed:
o Users: Stores user info.
o Products: Stores product details.
o Orders: Stores order history.
o Payments: Stores payment transactions.
• Use indexes for fast lookups.
• Implement ACID transactions for financial data.
• Use sharding for high-traffic scaling.

Question { 1118 }

How do you ensure database security?

Answer

• Use role-based access control (RBAC).
• Encrypt sensitive data using AES or SHA.
• Prevent SQL injection by using prepared statements.
• Enable audit logs for tracking changes.
• Use firewalls and secure authentication methods.