The snippet library.
Small, practical examples. Search by task or narrow things down below.
Enforce uniqueness with a dedicated index
SQL: A unique index rejects a duplicate combination independently of query plans.
SQL✓ Tested
Expose a reusable filtered view
SQL: A view stores a query definition rather than a snapshot of its rows.
SQL✓ Tested
Filter aggregate groups
Keep only categories with multiple products.
HAVING✓ Tested
Filter by a numeric comparison
SQL: Keep rows whose quantity exceeds a chosen threshold.
SQL✓ Tested
Filter groups after aggregation
SQL: Use HAVING to test a group’s calculated total.
SQL✓ Tested
Filter rows before grouping
SQL: WHERE limits the rows contributing to the aggregate; it differs from filtering completed groups with HAVING.
SQL✓ Tested
Filter rows with WHERE
Keep products below a chosen price.
WHERE✓ Tested
Find missing values with IS NULL
SQL: Use IS NULL rather than equality to test for missing data.
SQL✓ Tested
Find parents whose every child meets a rule
SQL: Combine existence with the absence of a violating child to exclude parents with no children.
SQL✓ Tested
Find parents with at least two child rows
SQL: Use a correlated count when testing a per-parent threshold.
SQL✓ Tested
Find records without any related rows
SQL: NOT EXISTS avoids the NULL pitfalls of NOT IN when the subquery column can be missing.
SQL✓ Tested
Find rows in the first result but not the second
SQL: EXCEPT calculates a distinct result-set difference.
SQL✓ Tested