Learn SQL

Ask better questions of relational data.

Start learning 6 lessons · about 1 hours · free
About this track

Learn how relational databases organize information, then build queries to retrieve, filter, summarize and connect data. You will also learn the care needed when changing records. SQL has several dialects (also called flavors): its core is shared, while features and syntax can differ between database systems. Exercises offer SQLite 3 and PostgreSQL 18 so you can compare two real engines.

Before you start
  • No programming experience needed.
  • A basic understanding of tables and spreadsheets is helpful but not required.
  • SQLite 3 is selected by default; choose PostgreSQL 18 from the dialect menu to run against that engine instead.
  1. Unit 1 · 0/2 lessons

    Relational foundations

    Understand tables and retrieve records. Badge: Data reader

    1. 0x001Meet relational dataRead tables, rows, columns and keys as the building blocks of a database. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
    2. 0x102Read data with SELECTChoose columns and a source table to retrieve useful records. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
  2. Unit 2 · 0/2 lessons

    Query and summarize

    Filter, order and aggregate query results. Badge: Query thinker

    1. 0x203Filter and sort resultsUse WHERE to select matching rows and ORDER BY to control their order. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
    2. 0x304Summarize with aggregatesCount rows, calculate totals and group records for comparisons. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
  3. Unit 3 · 0/2 lessons

    Relationships and changes

    Join tables and change records safely. Badge: Data steward

    1. 0x405Connect tables with JOINCombine related rows and learn what happens when a match is missing. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
    2. 0x506Change data with careInsert, update and delete records while protecting the rows you intend to keep. 12 min 0/1 exercises solved 12 min 0/1 exercises solved
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