Results for “empty”
Small, practical examples. Search by task or narrow things down below.
Filter rows before grouping
SQL Server: WHERE limits the rows contributing to the aggregate; it differs from filtering completed groups with HAVING.
SQL Server✓ Tested
Filter rows before grouping
Postgres: WHERE limits the rows contributing to the aggregate; it differs from filtering completed groups with HAVING.
Postgres✓ Tested
Find a sample range in one pass
Arduino / C: Initialize extrema from the first element of a nonempty array.
Arduino / C✓ Tested
Find both extremes in one algorithm call
C++: Check for a nonempty input before dereferencing the returned iterators.
C++✓ Tested
Find missing values with IS NULL
SQL Server: Use IS NULL rather than equality to test for missing data.
SQL Server✓ 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
SQL Server: Combine existence with the absence of a violating child to exclude parents with no children.
SQL Server✓ 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
SQL Server: Use a correlated count when testing a per-parent threshold.
SQL Server✓ Tested
Find parents with at least two child rows
Postgres: Use a correlated count when testing a per-parent threshold.
Postgres✓ Tested
Find records without any related rows
SQL Server: NOT EXISTS avoids the NULL pitfalls of NOT IN when the subquery column can be missing.
SQL Server✓ Tested
Find records without any related rows
Postgres: NOT EXISTS avoids the NULL pitfalls of NOT IN when the subquery column can be missing.
Postgres✓ Tested