How SQL DISTINCT and ORDER BY are Related
'One of the things that confuse SQL users all the time is how DISTINCT and ORDER BY are related in a SQL query.
The Basics
Running some queries against the Sakila database, most people quickly understand:
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SELECT DISTINCT length FROM film
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This returns results in an arbitrary order, because the database can (and might apply hashing rather than ordering to remove duplicates).
Most people also understand:
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SELECT length FROM film ORDER BY length
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This will give us duplicates, but in order.
And, of course, we can combine the two:
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SELECT DISTINCT length FROM film ORDER BY length
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'...
https://blog.jooq.org/2018/07/13/how-sql-distinct-and-order-by-are-related/
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