Memra
programming · beginner

PostgreSQL

Query real data — by writing real SQL

A complete, hands-on SQL course on real PostgreSQL running in your browser. From SELECT and JOIN to window functions, CTEs, upserts, schema design, and indexing — every concept is drilled by writing and running queries against one cohesive bookshop database.

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0 / 28 lessons

The Relational Model & First Queries

  1. Tables, rows, and your first SELECT 9 min
  2. Choosing columns (projection) 8 min
  3. Filtering rows with WHERE 9 min
  4. Sorting and limiting 8 min
  5. Removing duplicates with DISTINCT 6 min

Filtering Deeper

  1. Combining conditions: AND, OR, BETWEEN, IN 9 min
  2. Pattern matching with LIKE 8 min
  3. NULL and the unknown 9 min

Aggregating Data

  1. Counting and summarizing 9 min
  2. GROUP BY: per-category summaries 10 min
  3. HAVING: filtering groups 8 min

Joining Tables

  1. INNER JOIN: combining tables 10 min
  2. LEFT JOIN: keeping unmatched rows 10 min
  3. Joining three tables 10 min
  4. Aggregating across joins 10 min

Subqueries & CTEs

  1. Subqueries 10 min
  2. EXISTS and correlated subqueries 9 min
  3. Common Table Expressions (WITH) 10 min

Window Functions

  1. Windows: aggregates that keep the rows 11 min
  2. Ranking rows 10 min
  3. Running totals and LAG 11 min

Modifying Data

  1. INSERT (and RETURNING) 9 min
  2. UPDATE and DELETE 9 min
  3. UPSERT: INSERT … ON CONFLICT 10 min

Design & Performance

  1. Data types & constraints 10 min
  2. Normalization, briefly 9 min
  3. Indexes & EXPLAIN 10 min
  4. Capstone: a real report 12 min
NORMAL ~/memra/learn/postgresql utf-8 LF