Databases & SQL Skill

Overview

Master SQL and database concepts essential for data analysts, from basic queries to advanced optimization and data warehousing.

Core Topics

SQL Fundamentals

• SELECT, FROM, WHERE, ORDER BY
• JOINs (INNER, LEFT, RIGHT, FULL)
• GROUP BY and aggregate functions
• Subqueries and CTEs

Advanced SQL

• Window functions (ROW_NUMBER, RANK, LAG, LEAD)
• Recursive queries
• Query optimization and execution plans
• Index strategies

Database Concepts

• Relational database design principles
• Normalization and denormalization
• Data warehousing concepts (star schema, snowflake)
• ETL processes

Popular Platforms

• PostgreSQL
• MySQL
• SQL Server
• BigQuery, Redshift, Snowflake

Learning Objectives

• Write efficient SQL queries for data extraction
• Understand database design and optimization
• Work with cloud data warehouses
• Implement ETL processes for analytics pipelines

Error Handling

Error Type	Cause	Recovery
Syntax error	Invalid SQL	Validate query syntax before execution
Timeout	Long-running query	Add indexes, optimize query
Connection failed	Network/auth issue	Retry with exponential backoff
Permission denied	Access rights	Request appropriate permissions
Deadlock	Concurrent transactions	Retry transaction

Related Skills

• foundations (for data concepts)
• programming (for SQL with Python/R)
• advanced (for big data processing)