Results for “Relationships & missing data”
Small, practical examples. Search by task or narrow things down below.
Check for a hashtable key before reading it
PowerShell: ContainsKey distinguishes a missing key from a key whose value happens to be null.
PowerShell✓ Tested
Check JSONB containment
Test whether an object contains a key-value pair.
jsonb✓ Tested
Check whether a command can be resolved
PowerShell: Get-Command with a local error override supports an expected missing-command lookup.
PowerShell✓ Tested
Check whether a variable exists under nounset
Bash Scripts: The plus expansion distinguishes an unset variable without reading its missing value.
Bash Scripts✓ Tested
Check whether text is valid JSON
Reject malformed input before processing it.
json_valid✓ Tested
Choose a local file through a labeled control
HTML: A file input exposes selected file metadata to the page without providing arbitrary filesystem access.
HTML✓ Tested
Choose the signal used for graceful stopping
Docker / Compose: The configured stop signal is recorded in container metadata.
Docker / Compose✓ Tested
Collect ordered values into an array
Build a sorted array from query rows.
array_agg✓ Tested
Combine matching rows with INNER JOIN
Read product names with their matching stock values.
INNER JOIN✓ Tested
Combine results while retaining duplicates
SQL: UNION ALL does not spend work removing equal rows.
SQL✓ Tested
Combine results while retaining duplicates
SQL Server: UNION ALL does not spend work removing equal rows.
SQL Server✓ Tested
Combine results while retaining duplicates
Postgres: UNION ALL does not spend work removing equal rows.
Postgres✓ Tested