1. Beginner
Skills:
- Understanding basic SQL syntax and queries.
- Ability to create simple queries to retrieve data using
SELECT, WHERE, and ORDER BY clauses. - Familiarity with basic data operations like
INSERT, UPDATE, and DELETE. - Basic knowledge of filtering data with operators like
=, >, <, LIKE, and IN.
Example Tasks:
- Writing a query to select data from a table based on specific conditions.
- Sorting and filtering results using
ORDER BY and WHERE. - Inserting new rows into a table.
Skills:
- Proficiency with
JOIN operations (INNER, LEFT, RIGHT, FULL OUTER) to combine data from multiple tables. - Ability to group and aggregate data using
GROUP BY and aggregate functions (COUNT, SUM, AVG, MAX, MIN). - Understanding of subqueries and nested queries.
- Knowledge of database constraints (e.g., primary keys, foreign keys, unique constraints) and indexes.
- Experience with database normalization and designing relational database schemas.
Example Tasks:
- Joining multiple tables to retrieve related data.
- Writing queries to summarize data using group functions like
COUNT or SUM. - Creating database tables and defining relationships between them.
3. Advanced
Skills:
- Advanced query optimization techniques to improve query performance (e.g., indexing, query plans).
- Ability to write complex stored procedures, functions, and triggers.
- Proficiency in advanced SQL features like
WITH (CTE, Common Table Expressions) and window functions (e.g., ROW_NUMBER(), RANK()). - Knowledge of database transactions, ACID properties, and handling concurrency and isolation levels.
- Proficient in database security, user roles, and permissions management.
Example Tasks:
- Writing stored procedures and complex triggers to automate database operations.
- Optimizing slow queries by analyzing query plans and using appropriate indexing.
- Implementing transaction-safe SQL queries and managing concurrency.
4. Expert
Skills:
- Deep understanding of database architecture and internals (e.g., how indexes work, locking mechanisms, execution plans).
- Expertise in database design, partitioning strategies, and sharding for large-scale systems.
- Proficiency in advanced optimization techniques and tuning complex queries for performance.
- Ability to manage and configure database replication, backup, recovery, and high availability setups.
- Familiar with various database technologies (e.g., relational vs. NoSQL) and how to use SQL in different environments (e.g., cloud databases).
Example Tasks:
- Designing and implementing highly scalable database architectures for enterprise applications.
- Performing complex query optimization and database tuning for high-performance systems.
- Configuring and maintaining database clusters and replication systems.
