ORDER BY & LIMIT in SQL: Sort and Take the Top N
на канале: Unrote
Try it yourself. The full written explainer and an interactive visualizer are here:
https://unrote.com/sql/order-by-limit/
ORDER BY and LIMIT are how you sort and trim query results in SQL. This video builds both from zero, using one tiny customers table you can follow the whole way through.
What we cover:
Why rows come back in no guaranteed order without ORDER BY
ORDER BY to sort rows, ascending (ASC) and descending (DESC)
Sorting by more than one column to break ties
LIMIT to keep only the first few rows
The top-N pattern: ORDER BY ... DESC LIMIT N, for leaderboards and top spenders
OFFSET for paging through long lists
Where ORDER BY and LIMIT actually run in the query, plus two common traps
This is part of the Unrote SQL Foundations track. Every topic is taught from the ground up, with an interactive version on the site so you can run the queries yourself.
Chapters:
0:00 The hook: sort and trim
0:26 Two new clauses
0:42 No ORDER BY means no order
1:00 ORDER BY: sorting rows
1:17 ASC vs DESC
1:31 Sorting by two columns
1:50 LIMIT: keep just a few
2:04 The top-N pattern
2:24 OFFSET: paging results
2:42 When sort and trim run
3:02 Trap 1: LIMIT needs a sort
3:13 Trap 2: it differs by database
3:27 Recap
Understand it, don't memorize it.
https://unrote.com