Results for “Postgres”
Small, practical examples. Search by task or narrow things down below.
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
Find rows shared by two query results
SQL: INTERSECT compares complete selected rows and removes duplicates.
SQL✓ Tested
Find rows with a related record
Use EXISTS without duplicating the outer rows.
EXISTS✓ Tested
Find the second-highest distinct value
SQL: Select the maximum below the overall maximum to skip ties at the top.
SQL✓ Tested
Format a timestamp with to_char
Produce a fixed numeric date string.
to_char✓ Tested
Generate a sequence of numbers
Create rows without a stored table.
generate_series✓ Tested
Generate every combination of two sets
SQL: CROSS JOIN creates one result per possible pair, so the output size is the product of the input sizes.
SQL✓ Tested
Get the latest row in each group
Select one ordered row per key with DISTINCT ON.
DISTINCT ON✓ Tested
Give a result column a readable name
SQL: Use AS to label a computed result column.
SQL✓ Tested