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SQL · Lessons

SQL lessons

12 sections · 75 skills · work through the full outline skill by skill — read the long-form lesson or flip through the slide-style version.
Long-form lessonsSlide-style lessons

SQL

Practice 75 skills across this outline.

Recommended next
Normalization
Database Design
Long-form lesson
Weighting distribution
20 categories
Database Design
8%
SQL for Analytics and Reporting
8%
Performance and Optimization
8%
Window Functions
8%
SQL Foundations · Relational Data Concepts
6%
Subqueries and CTEs · Common Table Expressions (CTEs)
6%

Skills

The comprehensive taxonomy of sql — drill into a card to work its skills.

Database Design

3 core skills8% total weight
0/3 completed
3 skills to mastery
1
NormalizationRecommended
Long-form
2
Primary & Foreign KeysAvailable
Long-form
3
Many-to-Many ModelingAvailable
Long-form

SQL for Analytics and Reporting

4 core skills8% total weight
0/4 completed
4 skills to mastery
1
Communicating Query AssumptionsAvailable
Long-form
2
Defining & Implementing MetricsAvailable
Long-form
3
Parameterized Reporting QueriesAvailable
Long-form
4
Cohort & Segmentation QueriesAvailable
Long-form

Data Definition and Manipulation · DDL Basics

3 core skills4% total weight
0/3 completed
3 skills to mastery
1
CREATE TABLEAvailable
Long-form
2
ALTER TABLEAvailable
Long-form
3
Table ConstraintsAvailable
Long-form

Data Definition and Manipulation · DML Basics

4 core skills4% total weight
0/4 completed
4 skills to mastery
1
DELETE with WHEREAvailable
Long-form
2
INSERTAvailable
Long-form
3
TransactionsAvailable
Long-form
4
UPDATE with WHEREAvailable
Long-form

Aggregation and Grouping · Aggregate Functions

4 core skills5% total weight
0/4 completed
4 skills to mastery
1
Basic Aggregate FunctionsAvailable
Long-form
2
COUNT(*) vs. COUNT(column)Available
Long-form
3
Computing Derived AggregatesAvailable
Long-form
4
Aggregates with WHEREAvailable
Long-form

Aggregation and Grouping · GROUP BY and HAVING

4 core skills3% total weight
0/4 completed
4 skills to mastery
1
Grouping SetsAvailable
Long-form
2
GROUP BYAvailable
Long-form
3
HAVING for Group FilteringAvailable
Long-form
4
Avoiding Non-Aggregated ColumnsAvailable
Long-form

Data Transformation · Case Expressions and Conditional Logic

3 core skills4% total weight
0/3 completed
3 skills to mastery
1
COALESCE & IFNULLAvailable
Long-form
2
CASE WHEN for CategoriesAvailable
Long-form
3
Creating Flags & BucketsAvailable
Long-form

Data Transformation · String and Date Functions

3 core skills4% total weight
0/3 completed
3 skills to mastery
1
String FunctionsAvailable
Long-form
2
Date Range FilteringAvailable
Long-form
3
Date/Timestamp ParsingAvailable
Long-form

Data Quality and Debugging · Common SQL Pitfalls

4 core skills4% total weight
0/4 completed
4 skills to mastery
1
Integer Division in MetricsAvailable
Long-form
2
LEFT JOIN Filtering PitfallAvailable
Long-form
3
Join Duplication IssuesAvailable
Long-form
4
Three-Valued Logic & NULLAvailable
Long-form

Data Quality and Debugging · Validation and Sanity Checks

4 core skills4% total weight
0/4 completed
4 skills to mastery
1
Identifying DuplicatesAvailable
Long-form
2
Reconciling AggregatesAvailable
Long-form
3
Checking NULL RatesAvailable
Long-form
4
Validating Row CountsAvailable
Long-form

Joins and Relationships · Join Types and Keys

5 core skills5% total weight
0/5 completed
5 skills to mastery
1
Multi-Key JoinsAvailable
Long-form
2
Avoiding Join MistakesAvailable
Long-form
3
RIGHT JOIN & FULL OUTER JOINAvailable
Long-form
4
INNER JOINAvailable
Long-form
5
LEFT JOINAvailable
Long-form

Joins and Relationships · Multi-Table Joins and Self-Joins

3 core skills4% total weight
0/3 completed
3 skills to mastery
1
Bridge TablesAvailable
Long-form
2
Self-JoinsAvailable
Long-form
3
Multi-Table JoinsAvailable
Long-form

Performance and Optimization

3 core skills8% total weight
0/3 completed
3 skills to mastery
1
Indexes for PerformanceAvailable
Long-form
2
Index BasicsAvailable
Long-form
3
EXPLAIN/QUERY PLANAvailable
Long-form

Querying Data · SELECT and Filtering

5 core skills5% total weight
0/5 completed
5 skills to mastery
1
IS NULL / IS NOT NULLAvailable
Long-form
2
SELECT QueriesAvailable
Long-form
3
WHERE FilteringAvailable
Long-form
4
DISTINCTAvailable
Long-form
5
IN, BETWEEN & LIKEAvailable
Long-form

Querying Data · Sorting and Limiting

3 core skills3% total weight
0/3 completed
3 skills to mastery
1
Multi-Column OrderingAvailable
Long-form
2
LIMIT/TOPAvailable
Long-form
3
ORDER BYAvailable
Long-form

SQL Foundations · Relational Data Concepts

5 core skills6% total weight
0/5 completed
5 skills to mastery
1
Identifying KeysAvailable
Long-form
2
Tables, Rows & SchemasAvailable
Long-form
3
NULL & MissingnessAvailable
Long-form
4
Set-Based ThinkingAvailable
Long-form
5
Table RelationshipsAvailable
Long-form

SQL Foundations · SQL Query Structure

3 core skills2% total weight
0/3 completed
3 skills to mastery
1
Table AliasesAvailable
Long-form
2
SQL Logical OrderAvailable
Long-form
3
SQL Dialect DifferencesAvailable
Long-form

Window Functions

5 core skills8% total weight
0/5 completed
5 skills to mastery
1
Window Functions & GROUP BYAvailable
Long-form
2
LAG/LEADAvailable
Long-form
3
Running Totals & Moving AveragesAvailable
Long-form
4
Ranking FunctionsAvailable
Long-form
5
Windowed AggregatesAvailable
Long-form

Subqueries and CTEs · Subqueries

4 core skills3% total weight
0/4 completed
4 skills to mastery
1
EXISTS vs. INAvailable
Long-form
2
Correlated SubqueriesAvailable
Long-form
3
Subqueries in WHEREAvailable
Long-form
4
Scalar SubqueriesAvailable
Long-form

Subqueries and CTEs · Common Table Expressions (CTEs)

3 core skills6% total weight
0/3 completed
3 skills to mastery
1
Common Table Expressions (CTEs)Available
Long-form
2
Multiple CTEsAvailable
Long-form
3
Recursive CTEsAvailable
Long-form