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ORDER BY, LIMIT, DISTINCT and Aliases
ORDER BY, LIMIT, DISTINCT and Aliases ORDER BY sorts rows. LIMIT returns only a few rows. DISTINCT removes repeats. AS gives a column a new name. Attackers try ORDER BY 1, 2, 3… until the query breaks. That tells them how many columns it has. This is the first step of a UNION SQL injection. SELECT *
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What this card says
What it is
ORDER BY sorts rows. LIMIT returns only a few rows. DISTINCT removes repeats. AS gives a column a new name.
Why it matters for security
Attackers try ORDER BY 1, 2, 3… until the query breaks. That tells them how many columns it has.
This is the first step of a UNION SQL injection.
Common mistake
SELECT * on a huge table without LIMIT. It floods the screen and slows the server.
Learn more in the lesson: 10.6 ORDER BY, LIMIT, DISTINCT and Aliases