Learn SQL: Beginner's Guide to SQL

Beginner's guide to SQL covers basics of data manipulation and joining tables. Start exploring SQL for data analysis

By

Jatin Solanki

Updated on

November 14, 2024

Learn SQL: A Beginner's Guide to SQL

SQL, or Structured Query Language, is a programming language used to manage and manipulate data stored in relational databases. SQL is an essential tool for data analysts, data scientists, and software developers who work with large amounts of data. In this beginner's guide, we will walk you through the basics of SQL, including how to create, retrieve, update, and delete data, as well as join tables together.


Getting Started with SQL

Before you start writing SQL queries, you need to set up a database. There are several relational database management systems (RDBMS) that you can use, including MySQL, Oracle, and Microsoft SQL Server. You can install these RDBMS on your local machine or use a cloud-based service like Amazon Web Services (AWS) or Microsoft Azure.

Creating a Database

To create a database in MySQL, you can use the following SQL command:

This command will create a database named my_database. Once you have created a database, you can create tables to store your data.

Creating a Table

To create a table in MySQL, you can use the following SQL command:

This command will create a table named my_table with three columns: id, name, and age. The id column is set as the primary key, which means it will have a unique value for each row in the table.

Retrieving Data with SQL

Once you have created a database and a table, you can retrieve data from the table using the SELECT statement. Here's an example:

This command will retrieve all the data from the my_table table. If you only want to retrieve specific columns, you can list them after the SELECT keyword:

Updating Data with SQL

You can update existing data in a table using the UPDATE statement. Here's an example:

This command will update the age column for the row with the name John to 30. If you want to update multiple columns, you can separate them with commas:

Deleting Data with SQL

You can delete data from a table using the DELETE statement. Here's an example:

This command will delete all the rows from the my_table table where the name is John. If you want to delete all the rows in the table, you can omit the WHERE clause:

Joining Tables with SQL

One of the most powerful features of SQL is the ability to join tables together. Joins allow you to combine data from multiple tables based on a common column. There are several types of joins in SQL, including inner joins, left joins, right joins, and full outer joins.

Inner Joins

Inner joins return only the rows from both tables where the join condition is true. Here's an example:

This command will join the my_table table with the my_other_table table on the id column and return only the rows where there is a match between the two tables.

Left Joins

Left joins return all the rows from the left table and the matching rows from the right table. If there is no match in the right table, the result will contain null values for the columns from the right table. Here's an example:

This command will return all the rows from the my_table table and the matching rows from the my_other_table table. If there is no match in the my_other_table, the result will contain null values for the columns from my_other_table.

Right Joins

Right joins are similar to left joins, but they return all the rows from the right table and the matching rows from the left table. If there is no match in the left table, the result will contain null values for the columns from the left table. Here's an example:

This command will return all the rows from the my_other_table table and the matching rows from the my_table table. If there is no match in the my_table, the result will contain null values for the columns from my_table.

Full Outer Joins

Full outer joins return all the rows from both tables and match them based on the join condition. If there is no match in one of the tables, the result will contain null values for the columns from the table without a match. Here's an example:

This command will return all the rows from both the my_table table and the my_other_table table, and match them based on the id column.

Conclusion

SQL is a powerful tool for managing and manipulating data stored in relational databases. In this beginner's guide, we covered the basics of SQL, including how to create a database and a table, retrieve data, update data, delete data, and join tables together. With these skills, you can start exploring the vast world of SQL and using it to analyze and manipulate data.

External Links

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A Data Trust Platform is a unified framework that combines data observability, governance, lineage, and cataloging to ensure financial institutions have accurate, secure, and compliant data. In banking, it enables faster regulatory reporting, safer AI adoption, and new revenue opportunities from data products and APIs.
Why do AI initiatives fail in Latin American banks and fintechs?
Most AI initiatives in LATAM fail due to poor data quality, fragmented architectures, and lack of governance. When AI models are fed stale or incomplete data, predictions become inaccurate and untrustworthy. Establishing a Data Trust Strategy ensures models receive fresh, auditable, and high-quality data, significantly reducing failure rates.
What are the biggest data challenges for financial institutions in LATAM?
Key challenges include: Data silos and fragmentation across legacy and cloud systems. Stale and inconsistent data, leading to poor decision-making. Complex compliance requirements from regulators like CNBV, BCB, and SFC. Security and privacy risks in rapidly digitizing markets. AI adoption bottlenecks due to ungoverned data pipelines.
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Once data is governed and AI-ready, institutions can: Reduce OPEX with predictive intelligence. Offer hyper-personalized products like ESG loans or SME financing. Launch data-as-a-product (DaaP) initiatives with anonymized, compliant data. Build API-driven ecosystems with partners and B2B customers.
What is data dictionary example?
A data dictionary is a centralized repository that provides detailed information about the data within an organization. It defines each data element—such as tables, columns, fields, metrics, and relationships—along with its meaning, format, source, and usage rules. Think of it as the “glossary” of your data landscape. By documenting metadata in a structured way, a data dictionary helps ensure consistency, reduces misinterpretation, and improves collaboration between business and technical teams. For example, when multiple teams use the term “customer ID”, the dictionary clarifies exactly how it is defined, where it is stored, and how it should be used. Modern platforms like Decube extend the concept of a data dictionary by connecting it directly with lineage, quality checks, and governance—so it’s not just documentation, but an active part of ensuring data trust across the enterprise.
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How does MCP architecture work?
The MCP architecture operates under a client-server model: MCP Host: The AI application (e.g., Claude Desktop or VS Code). MCP Client: Connects the host to the MCP Server. MCP Server: Exposes context or tools (e.g., file browsing, database access). These components communicate over JSON‑RPC (via stdio or HTTP), facilitating discovery, execution, and contextual handoffs.
Why does the MCP Server matter in AI workflows?
MCP simplifies access to data and tools, enabling modular, interoperable, and scalable AI systems. It eliminates repetitive, brittle integrations and accelerates tool interoperability.
How is MCP different from Retrieval-Augmented Generation (RAG)?
Unlike RAG—which retrieves documents for LLM consumption—MCP enables live, interactive tool execution and context exchange between agents and external systems. It’s more dynamic, bidirectional, and context-aware.
What is a data dictionary?
A data dictionary is a centralized repository that provides detailed information about the data within an organization. It defines each data element—such as tables, columns, fields, metrics, and relationships—along with its meaning, format, source, and usage rules. Think of it as the “glossary” of your data landscape. By documenting metadata in a structured way, a data dictionary helps ensure consistency, reduces misinterpretation, and improves collaboration between business and technical teams. For example, when multiple teams use the term “customer ID”, the dictionary clarifies exactly how it is defined, where it is stored, and how it should be used. Modern platforms like Decube extend the concept of a data dictionary by connecting it directly with lineage, quality checks, and governance—so it’s not just documentation, but an active part of ensuring data trust across the enterprise.
What is the purpose of a data dictionary?
The primary purpose of a data dictionary is to help data teams understand and use data assets effectively. It provides a centralized repository of information about the data, including its meaning, origins, usage, and format, which helps in planning, controlling, and evaluating the collection, storage, and use of data.
What are some best practices for data dictionary management?
Best practices for data dictionary management include assigning ownership of the document, involving key stakeholders in defining and documenting terms and definitions, encouraging collaboration and communication among team members, and regularly reviewing and updating the data dictionary to reflect any changes in data elements or relationships.
How does a business glossary differ from a data dictionary?
A business glossary covers business terminology and concepts for an entire organization, ensuring consistency in business terms and definitions. It is a prerequisite for data governance and should be established before building a data dictionary. While a data dictionary focuses on technical metadata and data objects, a business glossary provides a common vocabulary for discussing data.
What is the difference between a data catalog and a data dictionary?
While a data catalog focuses on indexing, inventorying, and classifying data assets across multiple sources, a data dictionary provides specific details about data elements within those assets. Data catalogs often integrate data dictionaries to provide rich context and offer features like data lineage, data observability, and collaboration.
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Common challenges include resistance from business teams, lack of clear ownership, siloed systems, and tool fragmentation. Many organizations also struggle to balance strict governance with data democratization. The right approach involves embedding governance into workflows and using platforms that unify governance, observability, and catalog capabilities.
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AI and ML rely on high-quality, unbiased, and compliant data. Poorly governed data leads to unreliable predictions and regulatory risks. A governance framework ensures that data feeding AI models is trustworthy, well-documented, and traceable. This increases confidence in AI outputs and makes enterprises audit-ready when regulations apply.
What is data governance and why is it important?
Data governance is the framework of policies, ownership, and controls that ensure data is accurate, secure, and compliant. It assigns accountability to data owners, enforces standards, and ensures consistency across the organization. Strong governance not only reduces compliance risks but also builds trust in data for AI and analytics initiatives.
What is the difference between a data catalog and metadata management?
A data catalog is a user-facing tool that provides a searchable inventory of data assets, enriched with business context such as ownership, lineage, and quality. It’s designed to help users easily discover, understand, and trust data across the organization. Metadata management, on the other hand, is the broader discipline of collecting, storing, and maintaining metadata (technical, business, and operational). It involves defining standards, policies, and processes for metadata to ensure consistency and governance. In short, metadata management is the foundation—it structures and governs metadata—while a data catalog is the application layer that makes this metadata accessible and actionable for business and technical users.
What features should you look for in a modern data catalog?
A strong catalog includes metadata harvesting, search and discovery, lineage visualization, business glossary integration, access controls, and collaboration features like data ratings or comments. More advanced catalogs integrate with observability platforms, enabling teams to not only find data but also understand its quality and reliability.
Why do businesses need a data catalog?
Without a catalog, employees often struggle to find the right datasets or waste time duplicating efforts. A data catalog solves this by centralizing metadata, providing business context, and improving collaboration. It enhances productivity, accelerates analytics projects, reduces compliance risks, and enables data democratization across teams.
What is a data catalog and how does it work?
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How is data observability different from data monitoring?
Monitoring typically tracks system metrics (like CPU usage or uptime), whereas observability provides deep visibility into how data behaves across systems. Observability answers not only “is something wrong?” but also “why did it go wrong?” and “how does it impact downstream consumers?” This makes it a foundational practice for building AI-ready, trustworthy data systems.
What are the key pillars of Data Observability?
The five common pillars include: Freshness, Volume, Schema, Lineage, and Quality. Together, they provide a 360° view of how data flows and where issues might occur.
What is Data Observability and why is it important?
Data observability is the practice of continuously monitoring, tracking, and understanding the health of your data systems. It goes beyond simple monitoring by giving visibility into data freshness, schema changes, anomalies, and lineage. This helps organizations quickly detect and resolve issues before they impact analytics or AI models. For enterprises, data observability builds trust in data pipelines, ensuring decisions are made with reliable and accurate information.

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