uniqueonly

Uniqueonly is a term used in data processing to describe methods or filters that restrict data to elements deemed unique within a dataset. The exact meaning of 'uniqueonly' varies by context, but it generally refers to either displaying only values that occur once in a given field or presenting a set of distinct values with duplicates removed. In user interfaces, a 'unique only' control commonly labels a filter that hides repeated values.

In databases and data pipelines, unique-only can be implemented in two main ways. One interpretation is to retain only rows where the key attribute has a single occurrence in the current data snapshot (occurrence count equals one). This is often used for anomaly detection or data integrity checks. Another interpretation is to collapse a column to its distinct values, removing duplicates so each value appears once.

Implementation examples: In SQL, unique-only for a single attribute can be expressed with a subquery counting occurrences or with the HAVING COUNT(*) = 1 condition. In spreadsheet software, a 'Remove Duplicates' or 'Unique' filter yields a list of distinct values. In data-cleaning pipelines, a deduplication step may be parameterized to enforce either occurrence-based uniqueness or value-based distinctness, depending on the criterion.

Limitations include ambiguity in what counts as unique when nulls are present, how multi-column keys are treated, and performance considerations on large datasets. The term is descriptive rather than a formal standard, so definitions vary across tools and industries.

See also: distinct, deduplication, unique constraint, primary key, data cleansing.