majiayu000 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)