SQL Sorting and Limiting Results 5

Question 1

What does ORDER BY RANDOM() do in PostgreSQL?

Accepted Answer

Returns rows in random order

Answer

ORDER BY RANDOM() shuffles rows into a random sequence.

Question 2

Which gets a single random row efficiently in MySQL?

Accepted Answer

ORDER BY RAND() LIMIT 1

Answer

MySQL uses RAND() with LIMIT 1 to return one random row.

Question 3

When sorting strings of numbers stored as text, what happens?

Accepted Answer

They sort lexicographically (e.g., '10' before '2')

Answer

Text columns sort character-by-character, so '10' comes before '2'.

Question 4

What does ORDER BY 1 DESC do?

Accepted Answer

Sorts by the first SELECT column descending

Answer

The number 1 references the first column in the SELECT list, sorted descending.

Question 5

Which is generally faster than LIMIT/OFFSET for deep pagination?

Accepted Answer

Keyset (seek) pagination using WHERE on a sorted key

Answer

Keyset pagination filters by the last seen key, avoiding the cost of skipping rows.

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