Learn SQL, the same hands-on way

SQL is how analysts get data out of databases. Write real queries against a real database in your browser, and like the Excel lessons, every query is also tested on data you haven’t seen.

0 of 21 lessons done

1. SELECT

   1. Getting data out with SELECT

   Ask a table for the columns you want.

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2. WHERE

   2. Filtering rows with WHERE

   Return only the rows that match.

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3. ORDER BY, LIMIT and DISTINCT

   3. Sorting and limiting

   Put results in order, take the top few, and remove duplicates.

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4. LIKE, IN, BETWEEN and NULL

   4. Patterns, lists and missing values

   Flexible filters, and how to find what’s missing.

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5. Aggregate functions

   5. Summaries with COUNT, SUM and AVG

   Turn many rows into one number.

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6. GROUP BY and HAVING

   6. Grouping with GROUP BY

   A summary for each group, like a PivotTable.

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7. JOIN

   7. Combining tables with JOIN

   Pull related data together, like a lookup.

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8. Subqueries and UNION

   8. Subqueries and UNION

   Use one query’s result inside another.

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9. CASE

   9. Labels and buckets with CASE

   Turn values into categories inside a query.

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10. Text functions

    10. Working with text

    Change case, join and cut text.

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11. Arithmetic, ROUND and COALESCE

    11. Calculations and missing values

    Do maths in a query, and handle NULL.

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12. Self joins

    12. Joining a table to itself

    Find managers, and count their teams.

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13. Common table expressions

    13. Step by step with WITH

    Break a hard query into named steps.

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14. Window functions

    14. Rankings and running totals

    Rank rows and add running totals without grouping them away.

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15. EXISTS

    15. Checking for matches with EXISTS

    Find rows that do, or don’t, have a match elsewhere.

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16. INTERSECT and EXCEPT

    16. Combining results with INTERSECT and EXCEPT

    Find what two results share, or what one has that the other doesn’t.

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17. COUNT DISTINCT and GROUP_CONCAT

    17. Counting carefully

    Distinct counts, NULLs in counts, and lists in one cell.

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18. LAG and LEAD

    18. Comparing with the previous row

    Changes from one row to the next, and year-on-year growth.

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19. CREATE TABLE and CREATE VIEW

    19. Creating tables and views

    Define tables, add columns, and save queries as views.

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20. Putting it together

    20. Building reports

    Shares, complete lists and top customers.

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21. INSERT, UPDATE and DELETE

    21. Changing data

    Add, change and remove rows safely.

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