DISTINCT function (distinct spec)
The DISTINCT specification (
distinct_spec) is specified in a QUERY specification (query_spec), QUERY specification (named_query_spec), or SINGLE SELECT statement to remove duplicate rows.Syntax
<distinct_spec> ::= DISTINCT | ALL
Explanation
A row is a duplicate of another row if both have identical values in each column.
NULL values are assumed to be identical. Special NULLvalues are also assumed to be identical.DISTINCT: all duplicate rows are removed from the result table.
ALL: no duplicate rows are removed from the result table.
If no DISTINCT specification is specified, no duplicate rows are removed from the result table.