SQL

Introduction to SQL

Databases, tables and schemas, plus SELECT, filtering, and aggregation basics.

Filtering with WHERE

SELECT ... FROM, WHERE, comparison operators, AND/OR, IN, LIKE, BETWEEN, and DISTINCT.

Aggregate Functions & GROUP BY

COUNT, SUM, AVG, MIN, MAX, GROUP BY, HAVING, and aliasing.

ORDER BY & Dates

Sorting results, LIMIT, working with dates and timestamps, and extracting parts of a date.

AS & WITH (Common Table Expressions)

Aliasing with AS and organizing complex queries with WITH ... AS.

Joins

Combining tables with INNER, LEFT, RIGHT, and FULL JOIN.

Unions

Stacking results vertically with UNION and UNION ALL.

Subqueries

Queries nested inside other queries — scalar, IN, correlated, and EXISTS.

Window (Analytic) Functions

OVER, PARTITION BY, window frames, running totals, LAG/LEAD, and ROW_NUMBER/RANK.

Nested & Repeated Data (JSON)

Querying nested records and arrays — BigQuery STRUCT/ARRAY and JSON in SQL.

Views

Saving a query as a reusable virtual table.

Indexes

Speeding up lookups on large tables — and what indexes cost.

Writing Efficient Queries

Select only what you need, read less data, and avoid N:N joins.

Transactions

BEGIN, COMMIT, ROLLBACK, and keeping data consistent with ACID.