SQL
9 SQL lessons that turn up in real analyst work, three exercises each. Everything runs in your browser, so nothing is sent anywhere and there is nothing to install.
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SELECT & FROM
Ask for columns from a table, and read the query back as a sentence
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SELECT & WHERE
Pick the columns you want and drop the rows you do not
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ORDER BY & LIMIT
Put the rows in an order that means something, then take the top few
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DISTINCT
Ask what values exist without being handed the same one ten times
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COUNT, SUM & AVG
Turn a column of numbers into one number that answers the question
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GROUP BY
One row per region instead of one per order
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INNER JOIN
Two tables, one result, matched on the column they have in common
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CASE WHEN
Turn a number into a word people can actually read
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Subqueries
Let one query work out the number the other one needs
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