Results for “SQL”
Small, practical examples. Search by task or narrow things down below.
Expose a reusable filtered view
Postgres: A view stores a query definition rather than a snapshot of its rows.
Postgres✓ Tested
Extract a JSON field
Read a scalar value from JSON text.
json_extract✓ Tested
Extract part of a date
Read a calendar component with EXTRACT.
EXTRACT✓ Tested
Extract part of a string
Use one-based positions with substr.
substr✓ Tested
Filter aggregate groups
Keep only categories with multiple products.
HAVING✓ Tested
Filter by a numeric comparison
Postgres: Keep rows whose quantity exceeds a chosen threshold.
Postgres✓ Tested
Filter groups after aggregation
Postgres: Use HAVING to test a group’s calculated total.
Postgres✓ Tested
Filter rows before grouping
Postgres: WHERE limits the rows contributing to the aggregate; it differs from filtering completed groups with HAVING.
Postgres✓ Tested
Filter rows with WHERE
Keep products below a chosen price.
WHERE✓ Tested
Find missing values with IS NULL
Postgres: Use IS NULL rather than equality to test for missing data.
Postgres✓ Tested
Find parents whose every child meets a rule
Postgres: Combine existence with the absence of a violating child to exclude parents with no children.
Postgres✓ Tested
Find parents with at least two child rows
Postgres: Use a correlated count when testing a per-parent threshold.
Postgres✓ Tested