Competencies: Programming Languages > SQL

SQL Fundamentals

SELECT, INSERT, UPDATE, DELETE, WHERE, ORDER BY, LIMIT, basic queries

Critical

Backend Developer, Data Engineer, DBA

Joins & Relationships

INNER, LEFT, RIGHT, FULL, CROSS joins, self-joins, understanding cardinality

Critical

Backend Developer, Data Engineer, DBA

Aggregations & Grouping

GROUP BY, HAVING, COUNT, SUM, AVG, MIN, MAX, DISTINCT

Critical

Backend Developer, Data Engineer, Analytics Engineer

Subqueries & CTEs

Common Table Expressions, correlated subqueries, derived tables, recursive CTEs

High

Backend Developer, Data Engineer, Analytics Engineer

Window Functions

OVER, PARTITION BY, ROW_NUMBER, RANK, LAG, LEAD, running totals

High

Data Engineer, Analytics Engineer, Backend Developer

Indexes & Performance

B-tree indexes, covering indexes, index selection, EXPLAIN plans, query optimization

Critical

DBA, Backend Developer, Data Engineer

Transactions & ACID

BEGIN, COMMIT, ROLLBACK, isolation levels, locking, deadlock prevention

Critical

Backend Developer, DBA

DDL & Schema Design

CREATE, ALTER, DROP, constraints, foreign keys, normalization, denormalization

High

DBA, Backend Developer, Data Engineer

Stored Procedures & Functions

User-defined functions, stored procedures, triggers, cursors

Medium

DBA, Backend Developer

Dialect Differences

PostgreSQL, MySQL, SQLite, SQL Server specific features and syntax

High

Backend Developer, DBA, Data Engineer

JSON & Advanced Types

JSON columns, array types, full-text search, spatial data in SQL

Medium

Backend Developer, Data Engineer

To be populated

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